Many people have wondered what makes the oceans rise and fall on the word's beaches twice a day. Those tides are caused by the force of the Moon's gravity and the rotation  of the Earth. Gravity acts on the center of any solid object. The Earth is mostly molten  rock, but compared to the oceans, we can think of it as a solid object. As you know, the oceans are fluid and lie on the surface of the Earth. When the Moon is overhead, the oceans are four thousand miles closer to the Moon than the Earth's center is. Because the oceans are closer, the Moon pulls harder on the water than on the Earth. This stronger pull makes the water bunch up  a little under the Moon, creating a high tide. At the same time, the oceans on the opposite side of the Earth are four thousand miles farther from the Moon than the Earth's center is. The Moon's pull on this water is weak. This water bunches up because it is "left behind"(making another high tide) as the Earth is pulled slightly towards the Moon. When the waters bunch up on these two sides of the Earth, they draw water away from the other sides of the Earth, which creates the low tides. As the Earth rotates, different parts of the land and oceans pass through the high-tide and low-tide zones. And that makes the waters on our coasts go up and down. According to the passage, there would be no tides if there were no   _  .
Earth rotation gravity from the Earth gravity from the Moon Moon's gravity or Earth rotation
Question: Many people have wondered what makes the oceans rise and fall on the word's beaches twice a day. Those tides are caused by the force of the Moon's gravity and the rotation  of the Earth. Gravity acts on the center of any solid object. The Earth is mostly molten  rock, but compared to the oceans, we can think of it as a solid object. As you know, the oceans are fluid and lie on the surface of the Earth. When the Moon is overhead, the oceans are four thousand miles closer to the Moon than the Earth's center is. Because the oceans are closer, the Moon pulls harder on the water than on the Earth. This stronger pull makes the water bunch up  a little under the Moon, creating a high tide. At the same time, the oceans on the opposite side of the Earth are four thousand miles farther from the Moon than the Earth's center is. The Moon's pull on this water is weak. This water bunches up because it is "left behind"(making another high tide) as the Earth is pulled slightly towards the Moon. When the waters bunch up on these two sides of the Earth, they draw water away from the other sides of the Earth, which creates the low tides. As the Earth rotates, different parts of the land and oceans pass through the high-tide and low-tide zones. And that makes the waters on our coasts go up and down. According to the passage, there would be no tides if there were no   _  .
A. Earth rotation
B. gravity from the Earth
C. gravity from the Moon
D. Moon's gravity or Earth rotation
Answer: