I know that the answer will not be a or c due to effects of gravity. But I can't decide between b and d. I chose b because of lenzs law. I thought that since the south pole enter first, there will be an increasing flux upwards, coil opposes this by inducing an magnetic flux downwards. When it leaves, the north pole will cause and decreasing flux downwards, coil will then oppose this by inducing a magnetic flux downwards. Since both induced magnetic flux are downwards, the direction of induced emf will be the same. Am I correct??