A notable problem of air transportation in tropical Africa is

Analyze the question: It asks for a problem (a disadvantage) of air transport in tropical Africa. So we look for the option that describes a difficulty, not an advantage.

Concept: Air transport is the fastest mode, but it is also expensive and needs heavy investment in airports, aircraft, fuel and trained staff. In tropical Africa, the main challenges are:

• High cost of tickets and freight, so many people cannot afford it
• Low income levels among the population
• Poor airport facilities and high maintenance costs
• Small volumes of cargo and passengers compared with the huge cost of operation

Evaluate the options:

• A. Slow speed: Wrong. Air transport is the fastest mode of transport, so this is not a problem.
• B. Low freight charges: Wrong. Freight charges by air are high, not low, and low charges would be an advantage anyway.
• C. Adequate space: Wrong. Adequate space would be a benefit. Air transport actually has limited cargo capacity.
• D. Low patronage: Correct. Because fares are high and many people have low incomes, relatively few people use air transport. This makes it hard for airlines to make a profit, which is a well-known problem in tropical Africa.

Answer: D. Low patronage

Tip: In "problem of..." questions, remove any option that is actually an advantage (speed, adequate space, low charges). The one left that describes a difficulty is usually the answer. For air transport, remember: fast but costly, so few patrons.