练习：
1. What is the mystery that researchers find hard to explain?
A) Honeybees are flying all across the country.
B) 25-40 percent of the honeybees in the US have died.
C) Honeybees are leaving their hives and do not return.
D) Honeybee hives are in disorder.
2. Why are researchers seriously concerned with the phenomenon of colony-collapse disorder?
A) Because honeybees produce one-third of the foods we eat
B) Because honeybees feed on flowers.
C) Because honeybees eat seeds of flowers.
D) Both B and C.
3. What are the possible causes of colony-collapse disorder given by the scientists?
A) Worsening environment.
B) Disease and chemicals.
C) Dwindling number of flowers around.
D) Changes in genes’ structures.
4. According to the fifth paragraph， which of the following about bees’ genes is true?
A) Bees’ genes allow them to expand their colonies.
B) Bees genes help keep them in their hives.
C) Bees genes make them fly from flower to flower.
D) Bees genes could explain the collapse of some colonies.
5. What explanation is given by Jerry Hayes to the phenomenon?
A) Farmers apply certain chemicals to kill unwanted bees.
B)The insecticide destroys the honeybee’s nervous system.
C)The insecticide affects the honeybee’s memory.
D) All of the above.