கொடுக்கப்பட்ட மாற்றுகள் 1, 2, 3, 4 இல் இருந்து படம் X ஐ நிரப்பவும்

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.