Concept:Hydroelectric power projects are best constructed where there is an established need for more electricity to support development.
Explanation:Tropical Africa has rivers with waterfalls and receives abundant rainfall, which are suitable natural conditions for generating hydroelectric power.
However, the real reason to construct more of such projects is the steadily growing demand for electricity in the region.
Rapid population growth and expanding industrial activities are increasing the need for energy every year.
If there is a high demand for power, governments must build more projects to ensure adequate supply.
Options A and B are wrong because scanty rainfall and the absence of waterfalls would not support hydroelectric power generation.
Option C is also wrong because scarce skilled labour is a challenge to construction, not a reason for building more dams.
For this reason, the desire to satisfy the rising demand for power makes constructing more hydroelectric projects necessary.
Answer:D. There is an increasing demand for power.