Which of the following best explains why deforestation increases the risk of floods in an area?
a. tree leaves catch and retain rain water.
b. trees block the free flow of water.
c. deforestation increases precipitation.
d. tree roots improve soil water retention.

The correct answer is letter D.

Tree roots improve soil water retention that is why when deforestation on a massive scale is performed, areas are easily flooded and landslides along mountainous regions also occur. Cutting trees and not replacing them afterwards results to soil erosion, which can cause major destruction in certain geographical areas.