Which of the following statements about extinction is TRUE?

A)Overexploitation by hunting and fishing is the biggest threat to tropical animals and plants.
B)Without human activity,all species would survive and there would be no extinctions.
C)Wild species often become extinct due to different combinations of factors.
D)Commercial hunting and fishing are always careful not to deplete animal reserves.
E)Introduction of new exotic species should help increase biodiversity,slowing species extinctions.