题目内容

Since a new road________two years ago, this village has developed very fast.

A.builds B.built C.is built D.was built

练习册系列答案
相关题目

—Are there any questions about the hike?

—Yes, I want to know____ next Saturday.

A.when will Lisa go hiking with us B.if Lisa will go hiking with us

C.who will Lisa go hiking with D.that Lisa will go hiking with us

Could you please put some _________ in my cup? I’d like sweet coffee.

A.sugar B.salt C.ice D.pepper

A.What are the stamps used for?

B.Let’s come up with some good ideas.

C.Have you ever been late for school?

Bacterial Quorum Sensing

Bacteria(细菌)play an important role in our lives. They can keep us alive as well as make us sick. It wasn’t until fairly recently that we learned bacteria can communicate with one another.

In the 1960s, researchers found that a kind of bacteria called Vibrio fischeri（费氏弧菌） produced no light when they were alone, but that they exhibited great amount of light as the bacterial population grew to a certain number. How did this happen? How can Vibrio fischeri tell the difference between times when they’re alone and times when they’re in a community, and then all do something together?

Researchers found they talk to each other with a chemical language—signal molecules(信号分子). Vibrio fischeri makes signal molecules, and it also has a receptor on its surface that fits like a lock and key with a signal molecule. As the bacteria increase, more and more signal molecules are sent into the environment. When signal molecules increase to a certain amount, they lock down into those receptors and information comes into the bacteria, which tells them how many neighbors there are. As soon as they realize the population has hit the certain number, all of the bacteria behave as a group, making light together. In the past ten years, researchers have found all bacteria have systems like this: they make and recognize chemical words, determine(判断)the size of the community, and carry out tasks that would be unsuccessful if a single one were to act alone. This process is called quorum sensing.

Most of the time, bacteria live with thousands of other species (种类)of bacteria. There has to be a language of interspecies communication. In fact, bacteria have another kind of signal molecule, which is the common language used by all species. Moreover, this kind of molecule has its own receptor. In this way, bacteria are able to count different populations, and then they decide what task to carry out depending on which species has the greatest population.

Knowing how bacteria communicate could influence how we fight disease. What if bacteria can’t talk or hear? They won’t recognize when there are enough bacteria and when to exhibit the group behavior to make us sick. Researchers are developing a method—to make molecules that look like the real ones and then they lock into the receptors to jam recognition of the real situation.

On the other hand, researchers also improve the conversation of the beneficial bacteria, so they can do things that we want them to do better than they would do on their own.

1.According to the passage, what can we learn about quorum sensing?

A.Quorum sensing may happen when there is only one Vibrio fischeri.

B.Signal molecules are kept away from receptors during quorum sensing.

C.Most bacteria have similar systems to make light during quorum sensing.

D.Bacteria carry out a group task when their population hit a certain number.

2.What can we learn from the passage?

A.The more species there are, the more group actions bacteria will take.

B.In different environments, bacteria have different interspecies languages.

C.Beneficial bacteria communicate better by themselves than harmful ones.

D.To fight disease, researchers try to turn off the communication between harmful bacteria.

3.The passage is mainly about ________.

A.why bacterial population grows B.how bacteria communicate with each other

C.which bacteria help fight disease D.what scientists do to find quorum sensing

One of________challenges for people is to believe in themselves.

A.big B.bigger C.biggest D.the biggest

Here's all of the information you need to write on your party invitation. If it shows all of the facts about your party, 1.客人们将会觉得更容易做决定。They will be clear about if they can accept it or they have to turn it down.

The first thing you should put on your invitation is the name of the party host and the theme (主题) of the party. Your invitation should show the type of the party to the persons that you want to invite.

2.The next is the place where the party will be held. If your guests don't know about the address of the party, they may check the way to go without getting lost.

3. Clearly write the time of your party, with both date and day of the week. After checking the calendar, the guests will know if they are available on that day. 4.Your invitation also needs to tell your guests what time to arrive and how long the party will last (持续).

If you want your guests to reply to your invitation as soon as possible, you can give them a date by which you'll need an answer. 5.并且告诉他们一个电话号码或者一个电子邮箱地址 so that they can let you know.

1.______________________________________________

2.______________________________________________

3.______________________________________________

4.______________________________________________

5.______________________________________________

Jack is 18-year-old boy and he became university student 2 years ago.

A.an; a B.a; an C.an; an

There is always something unexpected in our life. I find it humorous sometimes that even the most ordinary thing can have an _______ on us.

My wife, daughter, and I moved into our home nine years ago and we _______ a lot of time and energy working in the yard to get it look like what it does today. We called this area our "rock garden" because there were so many rocks. We did the best we could to make the yard _______. Then, we started to grow plants and flowers and _______ them carefully.

Last summer I walked to the end of the rock garden and found a tiny little plant that I could not immediately tell what it was. I knew I didn't plant it and Denise said that she didn't _______. We decided to let it continue growing until we could _______ what it was.

Weeks passed and as I made my way back to the mystery (神秘的) plant, I found it grow taller. It appeared to be a Sunflower. As I pulled rocks from the area, I noticed something _______. The Sunflower didn't start where I saw the stalk (茎) begin. It actually began under a big rock and grew under and around it to _______ the sun.

Suddenly I realized something. "_______ a tiny little Sunflower has the ability of overcoming a big rock standing in its way of developing, we also have the ability of doing the same thing. "Like the Sunflower, it knew it had the ability to overcome difficulties.

Stand tall like the Sunflower and take ________in who and what you are and the environment will begin to support you. You will find a way to go under or around big difficulties in order to achieve your goal.

1.A.idea B.opinion C.experience D.influence

2.A.spent B.paid C.took D.cost

3.A.unclean B.tidy C.messy D.dirty

4.A.looked for B.looked after C.looked through D.looked over

5.A.too B.also C.either D.so

6.A.find out B.look out C.put out D.try out

7.A.interesting B.enjoyable C.ordinary D.unusual

8.A.hold B.reach C.catch D.have

9.A.Because B.Although C.If D.But

10.A.praise B.pride C.attention D.advice

违法和不良信息举报电话：027-86699610 举报邮箱：58377363@163.com

精英家教网