Let f be a function from the set of natural numbers to the set of even natural numbers given by f(x)=2x. Then f is

Options

A. one to one but not onto
B. onto but not one-one
C. both one-one and onto
D. neither one-one nor onto

Answer

C

Explanation

For each element in the domain there is only one element in the therefore f(x) is one-one.
No image in the co-domian which has no pre-image in the domian, therefore f(x) is onto
Hence f(x) both is one-one and onto.