Signals and Systems - Engineering

Q1:

Let f1(t) = G1(t) + 4, f2(t) = G2(t) + 3. If G1(t) and G2(t) are uncorrected then the correlation between f1(t) and f2(t) are

A 12

B 7

C 6

D zero

ANS:D - zero

How to solve this?