The correct answer is D) is formed by a temperature inversion. Radiation fog is caused by the cooling of the earth's surface on clear, calm nights, leading to the formation of a temperature inversion. As the ground cools, the air near the surface also cools, causing the water vapor in the air to condense and form a dense fog close to the ground. This fog is typically thickest near the surface and dissipates as you move away from the ground, which explains why it is formed by a temperature inversion. The other options are incorrect because: A) Radiation fog is thickest at the surface, not thinnest. B) Radiation fog can form over both land and water, not just over water. C) Radiation fog typically dissipates during the morning as the sun warms the ground, not in the evening.