The correct option is D px+px
Atoms come through Z - axis and Px, Py both lie in the X and Y axis respectively. X and Y are orthogonal to Z so either Px-Px can form Pi bond or Py-Py can form Pi bond.
Atoms acome along z axis, px and py both lie in the x and y axis respectively. x and y axis are orthogonal to z axis so conclusion is that either px- px or py - py can form π bond along z axis.