What conclusion can be drawn from the scientists observation？A．Insects have developed some

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.

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