6.(A)
This is not time-invariant.
1. input($ /delta[n-k] $) -> system -> time delay -> output : $ (k+1)^2/delta[n-(k+2)] $
2. input($ /delta[n-k] $) -> time delay -> system -> output : $ (k+2)^2/delta[n-(k+2)] $
The output signals are different each other. So this is not time-invariant.
