I am always eager to do experiments, especially chemistry ones. It's   _26_  to work with test tubes and beakers（烧杯） , even though sometimes my efforts end in__27___. Experiments were fun for me  __28  a recent accident.

The   29  happened when I was heating a big test tube with an alcohol burner（酒精灯） , chatting to my partner while waiting for__30____ changes. All of a sudden, the tube cracked. Even though I jumped from my seat when I heard the crack, the hair on my forehead was __31____ as I was leaning too close to the test tube.

  __32___ I had no time to be sad about my hair: the liquid in the test tube poured onto the table and caught fire. I'd never  33 _ anything so bad! My___34___went blank （空白）for a moment. Then I quickly covered the fire with a damp cloth to__35____.

The teacher told me that the test tube broke in half at the bottom because we didn't dry it properly before __36___ it.

We calmed down and did the experiment, again. But our hearts were still __37____ rapidly even after we walked out of the lab.

But my bad __38___ didn't end there! Since all __39     was focused on the flames while we were in the lab, I didn't see the liquid falling onto my trousers.

During the following class, I felt a __40___ in my leg. Soon it became more and more painful and I touched the area with my fingers,   _41_  to make things better. But to my great    42___ , the material of my trousers turned into powder! “Vitrio（硫酸）! ! !”The terrible word came into my mind. I rushed out right away to wash and examine my poor skin.  _43_  , it was not a serious injury.

After changing my __44____I sat down and told myself: danger is no joke! It's very important to have a serious___45___ in chemistry class. Doing scientific experiments as a learner is no laughing matter.

I am always eager to do experiments, especially chemistry ones. It's   21   to work with test tubes and beakers , even though sometimes my efforts end in failure. Experiments were fun for me   22   a recent accident.

     The accident happened when I was heating a big test tube with an alcohol burner , chatting to my partner. All of a sudden, the tube cracked. Even though I jumped from my seat when I heard the crack, the hair on my forehead was burnt as I was leaning too close to the test tube.

        23   I had no time to be sad about my hair: the liquid in the test tube poured onto the table and caught fire. I'd never  24   anything so bad! My mind went blank for a moment. Then I quickly covered the fire with a damp cloth to put it out.

     The teacher told me that the test tube broke in half at the bottom because we didn't dry it properly before 25  it.

      We calmed down and did the experiment, again. But our hearts were still   26   rapidly even after we walked out of the lab.

      But my bad luck didn't end there! Since all our   27   was focused on the flames while we were in the lab, I didn't see the liquid falling onto my trousers.

      During the following class, I felt a pain in my leg. Soon it became more and m6re painful and I touched the area with my fingers,   28   to make things better. But to my great   29  , the material of my trousers turned into powder! "Vitriol ! ! ! The terrible word came into my mind. I rushed out right away to wash and examine my poor skin.   30  , it was not a serious injury.

      After changing my trousers I thought it's very important to have a serious attitude in chemistry class. Doing scientific experiments as a learner is no laughing matter.

21. A. exciting    B. moving                     C. dangerous       D. difficult

22. A. but                B. except        C. besides               D. until

23. A. Because            B. Instead               C. But                    D. Or

24. A. felt                B. heard                       C. experienced     D. imagined

25. A. boiling        B. holding                 C. heating                 D. cooking

26. A. striking              B. beating                 C. knocking        D. hitting

27. A. effort               B. sense           C. attention          D. spirit

28. A. failing               B  imanaging             C. trying           D. planning

29. A. disappointment  B. joy              C. surprise       D. comfort

30. A. Luckily      B. Obviously               C. Unexpectedly           D. Generally

I am always eager to do experiments, especially chemistry ones. It's   _26_  to work with test tubes and beakers（烧杯） , even though sometimes my efforts end in__27___. Experiments were fun for me  __28  a recent accident.
The   29  happened when I was heating a big test tube with an alcohol burner（酒精灯） , chatting to my partner while waiting for__30____ changes. All of a sudden, the tube cracked. Even though I jumped from my seat when I heard the crack, the hair on my forehead was __31____ as I was leaning too close to the test tube.
  __32___ I had no time to be sad about my hair: the liquid in the test tube poured onto the table and caught fire. I'd never  33 _ anything so bad! My___34___went blank （空白）for a moment. Then I quickly covered the fire with a damp cloth to__35____.
The teacher told me that the test tube broke in half at the bottom because we didn't dry it properly before __36___ it.
We calmed down and did the experiment, again. But our hearts were still __37____ rapidly even after we walked out of the lab.
But my bad __38___ didn't end there! Since all __39     was focused on the flames while we were in the lab, I didn't see the liquid falling onto my trousers.
During the following class, I felt a __40___ in my leg. Soon it became more and more painful and I touched the area with my fingers,   _41_  to make things better. But to my great    42___ , the material of my trousers turned into powder! “Vitrio（硫酸）! ! !”The terrible word came into my mind. I rushed out right away to wash and examine my poor skin.  _43_  , it was not a serious injury.
After changing my __44____I sat down and told myself: danger is no joke! It's very important to have a serious___45___ in chemistry class. Doing scientific experiments as a learner is no laughing matter.

A microscope is a useful instrument for observing small objects. By producing a bigger image, the microscope reveals details that are undetectable to the naked eye(裸眼).

Before using the microscope, please read the instructions below.

CAUTION: Microscopes are both delicate and expensive and must be handled with care.

1. Always carry the microscope with two hands — one supporting the base and the other on the arm.

2. Avoid stretching the wire of the lamp across a walkway.

3. Keep the stage clean and always use a glass slide for specimens(样本).

4. To avoid crushing the glass slide when focusing, begin with the lens close to the specimen and gradually back off to focus.

5. Keep the microscope covered to prevent the dust while it is being stored.

HOW TO USE THE MICROSCOPE:

1. Plug(接通电源) in the lamp.

2. Place a sample of what you wish to observe on a slide.

3. Adjust the mirror so it reflects light from the room up into the objective lens. When the mirror is correctly adjusted, a complete circle of light iwll appear when you look through the eyepiece.

4. Place your slide with the specimen directly over the center of the glass circle on teh stage. If it is a wet slide, be sure the bottom of the slide is dry.

5. With the LOW POWER objective leans placed over the slide, use the coarse focus knob to lower the lens to the lowest point.

6. Look through the eyepiece with one eye while closing the other eye. Slowly raise the lens until teh focus is relatively clear.

7. Use the fine focus knob to fine -tune(微调)the focus.

8. Without changing the focus knobs, switch to the HIGH POWER objective lens. Once you have switched to HIGH POWER, use only the fine focus knob to make the image sharper.

1.Which of the following is the correct way to use a microscope according to the text?

A．Use one hand to carry the microscope

B．Place a sample directly on the clean stage

C．When stored, the microscope should be adjusted.

D．Look through the eyepiece with one eye.

2.If you want to observe a thin piece of hair, which of the following should you do first.?

A．Switch to objective lens.                  B．Adjust the mirror.

C．Look through the eyepiece.               D．Place the hair on a glass slide.

3.According to the text, you could see a complete circle of light _____.

A．after correctly adjusting the mirror

B．while looking at the specimen on a glass slide

C．after slowly raising the objective lens

D．before positioning the mirror correctly

A microscope is a useful instrument for observing small objects. By producing a bigger image, the microscope reveals details that are undetectable to the naked eye(裸眼).
Before using the microscope, please read the instructions below.
CAUTION: Microscopes are both delicate and expensive and must be handled with care.
1. Always carry the microscope with two hands — one supporting the base and the other on the arm.
2. Avoid stretching the wire of the lamp across a walkway.
3. Keep the stage clean and always use a glass slide for specimens(样本).
4. To avoid crushing the glass slide when focusing, begin with the lens close to the specimen and gradually back off to focus.
5. Keep the microscope covered to prevent the dust while it is being stored.
HOW TO USE THE MICROSCOPE:
1. Plug(接通电源) in the lamp.
2. Place a sample of what you wish to observe on a slide.
3. Adjust the mirror so it reflects light from the room up into the objective lens. When the mirror is correctly adjusted, a complete circle of light iwll appear when you look through the eyepiece.
4. Place your slide with the specimen directly over the center of the glass circle on teh stage. If it is a wet slide, be sure the bottom of the slide is dry.
5. With the LOW POWER objective leans placed over the slide, use the coarse focus knob to lower the lens to the lowest point.
6. Look through the eyepiece with one eye while closing the other eye. Slowly raise the lens until teh focus is relatively clear.
7. Use the fine focus knob to fine -tune(微调)the focus.
8. Without changing the focus knobs, switch to the HIGH POWER objective lens. Once you have switched to HIGH POWER, use only the fine focus knob to make the image sharper.
【小题1】Which of the following is the correct way to use a microscope according to the text?