The correct answer is A. The position of the moon with reference to the earth and the gravitational pull exerted mainly by the moon and partly by the sun.
Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon and the Sun and the rotation of the Earth. The gravitational pull of the Moon is stronger on the side of the Earth that is facing the Moon, and weaker on the side of the Earth that is facing away from the Moon. This difference in gravitational pull causes the Earth to bulge out slightly on the side facing the Moon, and to bulge in slightly on the side facing away from the Moon. These bulges of water are what we call tides.
The Sun also exerts a gravitational pull on the Earth, but its pull is much weaker than the Moon’s pull. This is because the Sun is much farther away from the Earth than the Moon is. However, the Sun’s gravitational pull does have an effect on the tides. The Sun’s pull is strongest when the Sun, Moon, and Earth are in a straight line, which is called a syzygy. During a syzygy, the tides are higher than normal. This is called a spring tide.
The tides are lowest when the Sun and Moon are at right angles to each other, which is called quadrature. During quadrature, the tides are lower than normal. This is called a neap tide.
The tides are also affected by the shape of the coastline. In some places, the coastline is very flat, and the tides are very small. In other places, the coastline is very steep, and the tides are very large.
The tides are an important part of the Earth’s natural cycle. They help to mix the water in the oceans, and they provide a source of energy for some types of marine life.