If Nx = {xn:n element N}, N5 intersection N7 is equal to a) N7 b) N c) N35 d) N12?

answer is N35..
i know how to calculate.

but same question with different options is given.
see these are options
N7
N5,
N
R

so, what would the answer then if in option N35 is not given????

Beats me -- if the answer is N35, why would the same question without that option be presented?