At one time or another most farmers have problems with mice. This is especially true for grain farmers. Mice eat a lot of grain. They also carry diseases(疾病), which people can get from eating or touching grain the mice have made dirty. Farmers can use special grain storage buildings or they can kill the mice. However, both methods can be costly. Farmers must buy materials to build the special grain storage buildings or chemical poisons to kill the mice．
Here is a way to kill mice without spending a lot of money. It is a simple but effective kind of mouse trap. The method is first used by some farmers in the west African country of Mali. An agricultural expert in Mali reported about the Mali mouse trap in a magazine. The expert reported that his gardener caught 150 mice in just one night. The gardener used four traps. The trap is easy to make. First, remove the top from a 20 liter metal or plastic container(容器). Put it in a hole in the ground. The top edge of the container should be the level with the surface of the ground. Fill the container with water to within eight centimeters of the top. Add tiny pieces of grain wastes. They should float on the water. Also put some wastes on the ground near the trap. During the night, mice will come out to eat the grain wastes. They will fall into the container and drown. Replace the food in the trap every night．
According to the passage，_____ used the mouse trap first.

A．an agricultural expert in the west Africa

B．farmers in the United States

C．all American gardener

D．farmers in Mali

What does the passage mainly tell us?

A．A simple and effective method used by farmers to kill mice

B．How to kill mice

C．Methods used by farmers to kill mice

D．Farmers have problems with mice

Which of the following can’t protect grain from being eaten by mice?

A．A special grain storage building

B．Chemical poisons

C．A mouse trap

D．A hole in the ground

Which is probably the trap mentioned in the passage?