Which geological feature on the Moon is similar to shallow, flat-bottomed riverbeds on Earth?

The correct choice is rilles, which are long, narrow depressions or channels on the Moon's surface, resembling shallow, flat-bottomed riverbeds found on Earth. These geological features are thought to have been formed primarily by ancient lava flows or tectonic processes, which allowed lava to carve out pathways similar to rivers. Rilles can vary in width and length and often exhibit a winding appearance, making them visually analogous to terrestrial riverbeds.

In contrast, regolith refers to the layer of loose, fragmented material covering solid bedrock on the Moon, which does not have the structured, channel-like characteristics of riverbeds. Breccia is a type of rock made up of broken fragments fused together, typically resulting from impacting events rather than fluid flow. Lastly, craters are large, bowl-shaped depressions formed by impacts from meteoroids or asteroids, needing no resemblance to riverbeds in their formation or structure. Therefore, rilles distinctly embody the features implied in the question.