If $(1+x)^n = C_0 + C_1x + C_2x^2 + ....+ C_nx^n$, then $C_0+2C_1 + 3C_2 + ....+(n+1)C_n$ is equal to :

Question

( A ) $2^n + n.2^{n-1}$
( B ) $2^{n-1} +( n-1).2^n$
( C ) $2^n+(n+1)2^n$
( D ) $2^{n-1} + n.2^n$