Concept:In tropical areas, seasonal changes are mainly marked by differences in rainfall rather than temperature.Explanation:Tropical regions lie near the equator, where temperatures remain high and fairly constant throughout the year.This means temperature alone does not create distinct seasons there.Instead, the movement of the Intertropical Convergence Zone brings alternating wet and dry periods.Therefore, rainfall is the main factor that determines the rainy season and the dry season in tropical areas.Answer:B. rainfall