Answer:
Option D
Explanation:
The coefficient of x9 in the expansion of
$(1+x)(1+x^{2})+(1+x^{3}).......(1+x^{100})$ = Terms having x9
= $[I^{99}.x^{9},I^{98}.x.x^{8},I^{98}.x^{2}.x^{7},I^{98}.x^{3}.x^{6}I^{98}.x^{4}.x^{5}$
$I^{97}.x.x^{2}.x^{6}I^{97}.x.x^{3}.x^{5}I^{97}.x^{2}.x^{3}.x^{4}]$
$\therefore$ coefficient of x9=8
