Which of the following reasons account for the low traffic on rivers in Africa?

Analyze the question: The question asks why African rivers carry little traffic (are of limited use for navigation and transport).

Explain the concept: For a river to be good for transport, it must be navigable over long stretches. This means it needs a steady depth, a gentle gradient, and no obstacles. Many African rivers flow over plateaus and drop sharply to the coastal plains. This creates rapids, cataracts and waterfalls that break navigation into short sections.

Examples:

• River Congo: Livingstone Falls block access from the sea.
• River Nile: cataracts between Khartoum and Aswan.
• River Niger: rapids such as those at Bussa.
• River Zambezi: Victoria Falls.

Other contributing factors include seasonal flow (shallow in the dry season) and sandbars or silting at the river mouths.

Step-by-step evaluation of the options:

• A. Presence of rapids and waterfalls: Correct. These obstruct continuous navigation, so ships and boats cannot travel far.
• B. Only used for fishing: This is a result, not a cause. Rivers are also used for irrigation, water supply and hydroelectric power.
• C. Wide valleys: Wide valleys do not hinder navigation. Wide, gently sloping river sections often help it.
• D. Change of colour during rainy season: The colour of the water has no effect on navigation.

Answer: The correct option is A.

Exam tip: When you see "low traffic/navigation on African rivers", think "RAPIDS and WATERFALLS = Roadblocks". Also remember related points such as seasonal flow and silting at river mouths, because they often appear in essay questions.