34,18,10,6,4,

Explanation :

In this equation each term is divided by 2 and afterward expanded by 1 to acquire the following term, just like :
34/2=17+1+=18
18/2=9+1=10
10/2=5+1=6
6/2=3+1=4
4/2=2+1=3


Final Answer :

Hence the correct option is C i.e. 3.