Question

transform boundaries involve plates past each other.

Explanation:

In the context of plate tectonics (a topic in Natural Science, specifically Geology which falls under Geography or Earth Sciences subfield), transform boundaries are where tectonic plates slide (or move) past each other horizontally. The correct verb here is "sliding" (or "moving") but the appropriate term to fill in the blank, based on plate tectonics knowledge, is that transform boundaries involve plates sliding past each other.

Answer:

sliding