Pi (π) bonds form by sidewise overlap of atomic orbitals perpendicular to the internuclear axis (x-axis here). For a π-bond, the orbitals must have a nodal plane containing the x-axis.

Let's evaluate the options:

• $d_{x^2-y^2}+d_{x^2-y^2}$: Overlap along axis → σ-bond.
• $p_x+p_x$: Overlap along axis → σ-bond.
• $d_{xy}+d_{xy}$: Lobe direction not perpendicular to x-axis.
• $d_{yz}+d_{yz}$: Lobes are perpendicular to x-axis, allowing sidewise overlap for π-bond formation.

Final Answer: d_yz + d_yz