Think about Keystone Species" and Trophic Cascades. What do I mean when I say that "some
animals are more equal than others"? Explain your
thinking.

all these collisions do one thing, and that thing is explained in the last option. when dusst, rocks and ice collide, they harden and form giant layers of rocks or hard ice.

d)   to harden materials to form different parts of earth’s layers

hope it ,

bioteacher101