If $C_0, \; C_1, \; C_2, ....$ are binomial coefficients, then $C_1 + C_2 +C_3 + C_4 + ..... + C_r +.... + C_n$ is equal to:

Question

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