问题详情

What conclusion can be drawn from the scientists observation？
A．Insects have developed some sort of resistance to man-made poisons.
B．Insects have been eating plants for about 250 million years.
C．Farmers sometimes use a combination of two or three insecticides at once.
D．New insects mate with insects which survived from a certain kind of insecticide.请帮忙给出正确答案和分析，谢谢！