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.
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.