If a vegetation map shows successive belts on mountains, what is the most suitable explanation?

Correct answer: Temperature and moisture are changing with altitude

The direct answer is C: successive vegetation belts on mountains are best explained by changes in temperature and moisture with altitude. As elevation increases, air generally becomes cooler, and slope exposure, cloud, precipitation, and available moisture may also change. Different plants tolerate different conditions, so one belt can replace another upward. Step by step: altitude rises; temperature usually falls; moisture and growing conditions vary; species suited to each zone form separate belts. Option C is correct and describes vertical zonation. A is wrong because vegetation belts are not evidence that state boundaries are changing. B is wrong because road direction does not create regular natural climate belts. D is wrong because plants are not all the same; their requirements differ. The exact pattern can vary by mountain and aspect, but altitude-related climate change is the sound explanation. Memory cue: mountain height changes climate, and climate changes vegetation.