Write the following sets in the set-builder form $B=\{2,4,8,16,32\}$

Question

$\begin{array}{1 1}(A)\;B=\{x : x=3^n,n\in N\;and\;n < 9\}\\(B)\;B=\{x : x=2^n,n\in N\;and\;n < 6\}\\(C)\;B=\{x : x=4^n,n\in N\;and\;n < 16\}\\(D)\;B=\{x : x=1^n,n\in N\;and\;n < 8\}\end{array}$