Which West African country has its north and south boundaries parallel a river?

• A. Mali
• B. Senegal
• C. Ghana
• D. Gambia

Answer: (D)

Rivers can define borders in a striking way, with a country’s edges tracing the course of a river. The Gambia fits this pattern because it is a very long, narrow country that sits along the Gambia River. The river runs from east to west through the country, and the land on both sides follows that path, so the northern edge and the southern edge run parallel to the river. That makes the river itself the defining feature of the country’s borders, which is why this choice is the best match. The other options don’t share this exact arrangement: their borders aren’t defined by a single river running along both the north and south edges.