Question

a ___ is a smaller river that flows into a single, larger river.
○ tributary
○ mesa
○ coast
○ basin
○ gulf

Explanation:

To solve this, we analyze each option:

• "tributary" is defined as a smaller river or stream that flows into a larger river or lake.
• "mesa" is a flat - topped hill, not related to rivers.
• "Coast" is the land along the edge of the sea, not a river - related term.
• "basin" is a depression or an area drained by a river system, not a smaller river.
• "gulf" is a large inlet from the ocean, not a river. So the correct term is tributary.

Answer:

A. tributary