Selecting a digital camera for personal use is no easy task because technology ______ so rapidly.  

A. is changing                   B. has changed

C. will have changed          D. will change

As is known to all, ______ great scientific achievements may have ______ positive effect on our life as well as society.  

A. /; a       B. the; a        C. the; /             D. /； /

Foods quickly spoil and break down if they are not stored correctly. Heat and damp encourage an increase of micro-organisms (微生物) ,and sunlight can destroy the vitamins in such foods as milk. Therefore, most foods should be stored in a cool, dark, dry place.

Some foods go had quickly, such as meat, eggs, and milk. They should be stored in a refrigerator or in the underground basement of a house.

Dry goods, such as flour and rice, should be kept a slightly higher temperathure than foods that go bad quickly. A temperature of 15℃ is ideal (理想的). In Britain and northem European countries this means that the room in which dry goods are stored should share the general heating of the house. The room should also be well aired and, above all, dry. Damp very quickly causes the growth of the green molds (霉) . These molds often grow on cheese if it is not stored properly.

Fruits and vegetables need cool, damp, but frost-proof (防霜冻的) conditions. Therefore, an underground basement usually makes an excellent storage place. If the central heating until is located in the basement, however, it will not be ideal unless the unit and the pipes do not give out any heat.

Foodstuffs (食料. 粮食) do not break down quickly. If correctly stored, they should keep for quite long periods of time. Thus, salt and sugar will keep for about two years; tinned meat goods, such as beef and chicken, for about eighteen months; flour and other dry goods, for about a year. Freezing the foodstuffs that spoil easily preserves them for much longer than is otherwise possible. But even frozen foods do not keep their food value of their taste for ever. As a general rule, meat should be cooked and eaten within a year afrer it is frozen; fish, within six to ten months; fruits and vegetables, within three to six months.

Three weeks ago, Paul Davis was given up for dead. Today the 24-year-old truck dirver is on the road to getting  36  , thanks to the quick,  37  first aid of six skilled college student nurses, who were travelling a few minutes  38  his truck and got to him  39  it crashed (撞坏).

The student nurses were on the way back from a day of medical  40  at a hospital. When they saw the  41  ,they jumped out of their car. They  42   that Davis was already dead, but they wouldn’t move on without seeing for  43  . With the help of three men, they lifted him out. He was bleeding  44  and his heart almost stopped beating. He was abviously  45  .

One girl found an ice-cream  46  on the ground and made an airway down his throat. Another student held his tongue down. Then a third girl found a towel (毛巾) and  47  down with it on Davis’ neck to slow the bleeding. A fourth nurse brought a blanket and  48  Davis to warm him up. They kept his legs  49  . “We kept talking to him,” Miss Taylor said. “We  50  that the last thing you lose is your  51  .”

The student nurses kept Davis  52  until he could be sent to hospital. There, he brought out of  53 . A doctor said that Davis would have choked and bled to death without the  54  of the six student nurses. That is  55  he is alive today.