When the Rodenticide Warfarin Was First Introduced,rats Were Very Susceptible

Multiple Choice

When the rodenticide warfarin was first introduced,rats were very susceptible to it.The development of resistance to warfarin by rats was the result of  

A) the development of other blood clotting factors.
B) natural selection of individuals that had a beneficial mutation.
C) the high biotic potential of rodents.
D) inheritance of acquired characteristics.
E) mutation induced by warfarin.