The Central African peoples have lived in the tropical rainforests for thousands of years. During most of that time, they have used the forest for most of their needs and have changed their style of living based on what the rainforest gave them. People of the rainforest have used the timber in the rainforest to build their homes and to burn as firewood. They have used plants as medicine and food. In the past, most of these indigenous people were seminomadic, moving their villages when they needed to find new food supplies or to find higher ground during floods. This passage is an example of -

A. the use of natural resources to control the environment
B. how the rainforest can provide valuable medicines
C. diffusion of peoples caused by natural events
D. human adaptation and modification of the environment