Correct Option
The correct option is 20°C.
Explanation
The Tropical Wet Climate (designated as Af in the Köppen climate classification), also known as the Equatorial Climate, is found between 5° and 10° North and South of the equator. It is characterized by uniformly high temperatures and heavy precipitation throughout the year, with no distinct winter season.
Detailed Analysis
- Temperature Characteristics: In this climate zone, the sun is vertically overhead throughout the year, resulting in intense insolation. The annual range of temperature is negligible (often less than 3°C).
- Minimum Thresholds: According to standard physical geography texts (such as G.C. Leong), the temperature is uniformly high. The mean monthly temperature is always above 18°C. Specifically, the thermometer rarely records a temperature below 20°C (68°F), even at night.
- Comparison with Options:
- 10°C and 15°C: These temperatures are too low for a lowland equatorial climate and are characteristic of temperate zones or high-altitude regions.
- 25°C: This figure is closer to the mean daily temperature (typically around 27°C) rather than the minimum.
Key Takeaway: In the Tropical Wet Climate (Af), the temperature is consistently high year-round, with night-time minimums typically remaining around 20°C and rarely dropping below this threshold.