For how long have the heavy rains been falling

A．Because farmers use less insecticides now.
B．Because farmers have been using insecticides for many years.
C．Because insects arc using the mechanisms against poisons produced by plants to deal with insecticides.
D．Because insects have been eating plants for many million years.

A．Insects are the most adaptable creatures.
B．Insects would be out of control if nothing were done about the current situation.
C．Insects will someday devour all plants on the Earth.
D．Insects have developed resistance to both botanical and artificial poi- sons rapidly.