What is the total number of p electrons in a single phosphorus atom in its ground state?

The total number of p electrons in a single phosphorus atom in its ground state is 9.

Phosphorous's electrical configuration is $1s^{2}2s^{2}2p^{6}3s^{2}3p^3$

Consequently, the total number of $p$ electrons is $6 + 3 = 9$

Hence, option C is correct.