Which of the following examples poses the greatest potential threat to biodivers

Which of the following examples poses the greatest potential threat to biodiversity?

A) releasing sterilized rainbow trout to boost the sport fishing of a river system that contains native brook trout
B) allowing previously used farmland to go fallow and begin to fill in with weeds and then shrubs and saplings
C) replanting, after a clear cut, a monoculture of Douglas fir trees on land that consisted of old-growth Douglas fir, western cedar, and western hemlock
D) trapping and relocating large predators, such as mountain lions, that pose a threat as they move into areas of relatively dense human populations
E) importing an Asian insect into the United States to control a weed that competes with staple crops