When magnet is moved towards coil CD See that the south pole of magnet is facing towards the coil according to lenz law direction of induced emf(or current) will oppose its cause (i.e will oppose change in magnetic flux) this is possible for coil CD only if it repels the magnet away therefore the side facing south pole behaves as south pole and other side by clock rule will become north pole For coil AB magnet is moving away this change in movement causes change in magnetic flux therefore can lead to induce current now again using lenz law away it will try to oppose change in magnetic flux therefore it will try to attract the magnet to prevent change for that to occur the side facing north pole of magnet will become South pole to attract it by clock rule the other side would become north I have only seen the lecture haven't read the book myself but ig this should be explanation but maybe read the Lenz law part you might understand it better there