A Level physics Magnet field question (1)

For this question I understand the theory that I am meant to use i.e a change in magnetic flux induces a emf but visually how do I know the magnetic flux is changing? I got 3 as I thought the second, third and fourth option would cause a change in flux why is that not true ?
The answer is A btw

Why do you think options 2, 3 and 4 would give rise to a change in magnetic flux?

2) because as it moves towards Y its cutting through new lines ? but I guess the number of line in its area remains roughly the same is that why there's no change in flux ? So as long as the the field lines are uniform and the number of field line remain the time in the area there's no change in flux is that correct ?

-3 and 4 I get why I was wrong with those ones now but originally I thought that as it spins it's constantly cutting though the field lines so I just assumed that means there would be a change in flux leading to a induced emf