Find the number of $\mathrm{p}-\mathrm{p}$ linkages in ${\mathrm{P}}_4{\mathrm{S}}_3$. 

The structure of ${\mathrm{P}}_4{\mathrm{S}}_3$ can be given as,

Here, the $\mathrm{p}-\mathrm{p}$ are 3 which can be seen in the above figure.

Thus, the correct answer is 3.