# The structure of $N(CH_3)_3$ and $N(SiH_3)_3$ are respectively

$\begin{array}{1 1}(a)\;\text{trigonal planar and pyramidal}\\(b)\;\text{ pyramidal and trigonal planar}\\(c)\;\text{ both pyramidal}\\(d)\;\text{ both trigonal planar}\end{array}$

pyramidal and trigonal planar
Hence (b) is the correct answer.