Answer:
B.

Explanation:
A. y = x
Given a linear function. There is no number added or subtracted with x. also the number is no multiplied with x. So this is a parent function
B.

Here 2 is multiplied with
. so there will be stretch or compression on graph. The parent function for
is

This is not an example of parent function
C.

There is no number attached with x. so this is a parent rational function.
D.

2^x is an exponential function. It is an example of parent function.