In this question, we are trying to understand where the height of the ocean tide would be maximum, given four different positions: M1, M2, M3 and M4.

Given that the correct answer is `M4`, it`s presumed that the diagram (which is not provided here) indicates that the tide would be highest at position M4. This might possibly be due to gravitational forces at work, as tides are caused by the gravitational pull of the Moon and the Sun on Earth`s waters.

Without seeing the diagram, it`s difficult to explain precisely why M4 is the correct answer, but maybe position M4 is directly aligned with the moon, which would cause a high tide due to strongest gravitational pull.

In the case of Options M1, M2, and M3: If these are different positions around the Earth, then depending on their relative positions to the Moon and the Sun, the height of the tides would vary. The tide would be lower when the positions are not directly aligned with the Moon, which is presumably the case for M1, M2, and M3.