[Corribus]

Ok, let's review:

The 3 p_z orbitals on the 3 chlorines belong to symmetry groups:

A"₂ and E"

The s orbital on the central P atom belongs to symmetry group A'₁.
The p_x, p_y, and p_z orbitals on the central P atom belong to E" for p_x,p_y and A"₂ for p_z.
The d_x2-y2 and d_xy orbitals on the central P atom transform together as E'. The d_z2 orbital transforms as A'₁. And the d_xz and d_yz orbitals transform together as E".

So, look for matches.

A"₂ of the 3 chlorine p_z orbitals matches with the p_z orbital on the central P atom.

E" of the 3 chlorine p_z orbitals matches with the (d_xz,d_yz) transform. So your answer is the p_z and d_xy,d_yz atomic orbitals on the central P atom.

Now, if you think about the fact that in order to interact, orbitals have to be aligned correctly, this makes sense. Obviously the p_z orbital on the central atom should be able to act with the p_z orbitals on the chlorines. The doubly degenerate representations are a little harder to picture, but again if you consider the way that the d_xz and d_yz orbitals on the central atom are aligned, you should be able to visualize how they might interact with the p_z orbitals on the chlorines. Compare that to, for example, the d_xy orbital, which is in the molecular plane - there's no way it can realistically interact with the 3 p_z chlorine orbitals.

[shafaifer]

Thank you for great help, Corribus.