TOEFL Reading: ETS-TOEFL阅读机经 - S564CM1831877M68L$

What can be inferred from paragraph 1 about nonindigenous pests such as brown rats and cockroaches? A. Attempts limit the size of their populations have been unsuccessful. B. They have inhabited North America longer than white-footed mice and ground moles. C. Their numbers cannot usually be controlled by native predators and parasites. D. They do not pose as many problems for humans as do white-footed mice and ground moles.