Which of the following has planar shape with respect to the central atom?

The molecules which has the planer shape geometry with respect to central atom is, $\mathrm{N}{\left({\mathrm{SiH}}_3\right)}_3$

In $\mathrm{N}{\left({\mathrm{SiH}}_3\right)}_3$ lone-pair on N−atom is transferred to the empty d− orbitals of silicon (pπ−dπ) overlapping.
Thus, option C is correct.