Describe the effect on the heights of earth’s high and low tides when the moon moves from position d to position a.

Well, something that will hhelp you see the effect on the heights of earths hicch and low tides is the fact that  the Moon's gravitational forces are strong enough to disrupt the balance of the waters by accelerating the water towards the Moon. As the Moon orbits our planet and as the Earth rotates, the waters of the earth also moves. So, in some areas, like in the D position, the waters are in high tides and in the A part will be low tides.