ans-c
from basic, consider one sender , he send to four other who only read
" two " they send to seven other "
" three " they send to ten other receiver who only read
this form AP having comman difference 3, and a/q total number of reciever who only read is 100 that is our last term
so, 4+(n-1)*3=100
n=33 this is the no. of reader who send to four other
already there are 100 viewer who only read
so total viewer will be 33+100=133