The correct answer is A. the monsoon climatic regions.
Monsoon climatic regions are characterized by a wet season and a dry season. The wet season is caused by the monsoon winds, which blow from the ocean to the land. The dry season is caused by the trade winds, which blow from the land to the ocean.
Monsoon climatic regions are located in the tropics, between the Tropic of Cancer and the Tropic of Capricorn. The most densely populated monsoon climatic regions are in Asia, Africa, and South America.
The equatorial regions are located around the equator. The equatorial regions are characterized by a hot, humid climate. The equatorial regions are not as densely populated as the monsoon climatic regions.
The hot desert climatic regions are located in the subtropics. The hot desert climatic regions are characterized by a hot, dry climate. The hot desert climatic regions are the least densely populated regions in the world.
The summer climatic regions are located in the temperate zones. The summer climatic regions are characterized by a warm, humid climate in the summer and a cold, dry climate in the winter. The summer climatic regions are not as densely populated as the monsoon climatic regions.