We can take measures to reduce the risk of mass wasting. The accompanying diagram illustrates one technique to help protect a road. What is it, and how does it help? Choose one or more:

A. A retaining wall can trap falling rock, protecting a road from a rockslide.
B. Bolting or screening a cliff face can hold loose rocks in place, preventing a rockslide.
C. An avalanche shed diverts debris or snow over a roadway.
D. Terrace steps can remove load and catch debris on a slope and help stabilize it.