The coefficient of $$x^{48}$$ in $$ (1+x) + 2(1+x)^{2}+3(1+x)^{3}+....+100(1+x)^{100} $$ is equal to

A

$$100\cdot ^{101}C_{49}-^{101}C_{50}$$

B

$$100\cdot ^{101}C_{49}-^{101}C_{48}$$

C

$$ ^{100}C_{50}-^{101}C_{49}$$

D

$$100\cdot ^{100}C_{49}-^{100}C_{50}$$