'A' and 'B' are two sets such that n(A) = 4 and n(B) = 2. If a relation from A to B is selected at random, then the probability that their relation is not a function is

A

$$\frac{7}{8}$$

B

$$\frac{1}{16}$$

C

$$\frac{3}{16}$$

D

$$\frac{15}{16}$$