दिए गए विकल्पों 1, 2, 3, 4 में से कौन सा, आकृति X की पूर्ती करता है?

The missing top-left piece must fit its neighbours: the piece below has a knob pointing up, so the missing piece needs a socket at the bottom; the piece on the right has a socket on its left side, so the missing piece needs a knob on its right. Only option 2 (knobs left and right, sockets top and bottom) fits both.