If a river has its source in high mountains and mouth on a shallow calm coast, which sequence is more likely?

Correct answer: Upper erosion and lower deposition

The direct answer is A: the likely sequence is upper-course erosion followed by lower-course deposition. A river starts high in the mountains, where the slope is steep. Gravity makes the water flow fast, giving it strong energy to cut and remove rock and soil. This is erosion in the upper course. As the river reaches a shallow, calmer coast, the slope and speed decrease. The river loses carrying power and drops sand, silt and clay, producing deposition and often deltaic features. Therefore option A matches the physical sequence. Option B is wrong because deltas usually form near a river mouth, not in the steep upper course, while gorges are more typical of youthful, high-relief areas rather than the calm lower coast. Option C is wrong because a river normally carries water and does not remain dry everywhere. Option D is wrong because every river does not form an estuary; a shallow, calm, sediment-rich mouth is more favourable for deposition or a delta. The key chain is steep slope and fast flow equals erosion; gentle slope and slow flow equals deposition.