Which of the following best explains how human activities can directly contribute to landslides? a. removing plants from hillsides eliminates the root structures that anchor soil. b. clearing trees from hills increases the frequency of rainstorms. c. human activities tend to reduce the risk of fires. d. landslide are not impacted by human activities.

The answer is the option a. removing plants from hillsides eliminates the root structures that anchor soil. Indeed the roots of trees, further to anchor the tress to the floor, serve as a net to which the soil attaches preventing the soil of been washed and removed by rainstorms, other natural events or even other human activities that cause erosion. .