Final answer:
Equatorial regions have the smallest annual temperature ranges, around 5 degrees Celsius, due to the constant sunlight and oceanic influences. Greenhouse gases also contribute to maintaining the Earth's relatively stable climate.
Step-by-step explanation:
The areas where the annual temperature ranges are the smallest, typically around 5 degrees Celsius, are found in the equatorial regions, particularly in oceanic and coastal locations. These regions have very stable climates due to the consistent presence of sunlight throughout the year and moderating effects of the ocean. As the Earth's surface is heated unevenly, areas close to the equator receive a fair amount of sunlight all year round, leading to minor variations in daily and seasonal temperatures.
Moreover, the influence of greenhouse gases, notably water vapor (H₂O), plays a substantial role in maintaining the earth's suitable average temperature by trapping heat within the atmosphere and preventing most of the radiation from escaping directly into space, which would otherwise lead to more extreme temperatures.