What is the structure and hybridization of $Si(CH_3)_4$?

Which of the following can have a structure with $sp^3$ $C$ atoms only?

Discuss the hybridization and shape of $PCl_5$.

The mean values for the radial distance for different phosphorus orbitals are $3s: 0.47 \ \mathring{A}$,$3p: 0.55 \ \mathring{A}$,$3d: 2.4 \ \mathring{A}$. When $P$ is going to form $PF_5$,then these radial distances are going to become arbitrarily . . . . . . , . . . . . . and . . . . . . respectively.

In which hybridisation is an angular shape not possible?

What is the type of hybridization of $N$ in $NH_3$?