Farmers can produce more by planting several different crops in the same field. But their success depends on which crops they plant together and how they mix (混合) them in the filed. Until now, the only way the farmers could learn which crops grow best together is to plant them and wait for the results. Now, however, a computer can give them answers. A new computer program written by Dr John Vanderwell of Michigan University can tell a farmer which plants grow well together and which do not. It can tell him how to plant the different crops; if he should plant each in a separate row, or mix the crops in the same row. It can tell the farmer how changes in planting each of the crops will affect the production of all of them. And it can tell him which plants can help reduce losses（损失）from diseases.
36. Which of the following best gives the main idea of the passage? A. Computer helps find the best program for mixing plants. B. Computer helps produce more crops.
C. Computer helps protect against insects and diseases. D. Computer helps grow different plants.
37. According to the passage, to get the best result, one needs to choose carefully . A. the kinds of crops to be planted together B. the way for different crops to be mixed C. both A and B D. either A or B
38. It seems the new computer program can NOT tell us . A. whether we should grow cotton and tomato together B. how we should plant cotton and tomato together
C. what will happen if we grow potato, instead of tomato, together with cotton D. how we can grow rice in the tomato field
39. The new computer program seems most useful in saving us . A. man power B. seeds C. time D. land
40. Which of the