The smallest annual temperature range occurs in the

equatorial tropical climate zone
subtropical climate zone
temperate climate zone
polar climate zone

The correct answer is: A. equatorial tropical climate zone.

The equatorial tropical climate zone is located near the equator, where the sun’s rays are most direct. This means that the temperature is relatively constant year-round, with little variation between day and night or between summer and winter.

The subtropical climate zone is located between the tropics and the temperate zones. The sun’s rays are less direct in this region, so there is more variation in temperature between day and night and between summer and winter.

The temperate climate zone is located between the subtropical zones and the polar zones. The sun’s rays are even less direct in this region, so there is even more variation in temperature between day and night and between summer and winter.

The polar climate zone is located near the poles, where the sun’s rays are very indirect. This means that the temperature is very cold year-round, with very little variation between day and night or between summer and winter.