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Scientists have increased the size of crops by 20 percent. They have changed how plants use photosynthesis(光合作用). This is when plants use sunlight to change carbon dioxide into oxygen. A professor said he is changing the genes(基因) of crops like rice, wheat, maize and soybean. The new plants use the energy from sunlight better.

Plants change energy into heat when they get hot. They also do this when it is cloudy. The scientists changed their genes, so plants can use more energy to grow. If crops can give 20 percent more food, it will help us have more food in the future.

1.Plants use _____ to change carbon dioxide into oxygen.

A air

B sunlight

C soil

D earth

解析：选B。细节理解题。根据第一段第三句This is when plants use sunlight to change carbon dioxide into oxygen. 可知，故选B。

2.If scientists change the genes of plants, the new plants use the energy from sunlight _____.

A better

B longer

C bigger

D taller

解析：选A。细节理解题。根据第一段最后两句A professor said he is changing the genes of crops like rice, wheat, maize and soybean. The new plants use the energy from sunlight better.可知，故选A。

3.Which crops’ genes will be changed?

A The genes of peanut, maize and soybean.

B The genes of rice, peanut and soybean.

C The genes of wheat, maize and soybean.

D The genes of rice, wheat and peanut.

解析：选C。细节理解题。根据第一段倒数第二句A professor said he is changing the genes of crops like rice, wheat, maize and soybean.可知，故选C。

4.Why can plants use more energy to grow?

A Because scientists get new sunlight.

B Because scientists get new soil.

C Because scientists change their genes.

D Because scientists change the water.

解析：选C。推理判断题。根据第二段第三句The scientists changed their genes, so plants can use more energy to grow.可知，故选C。

5.If crops can give ______ more food, it will help us have more food in the future.

A 20 percent

B 30 percent

C 40 percent

D 50 percent

解析：选A。细节理解题。根据文章最后一句可知，故选A。