Which factor most likely explains the difference in tectonic activity between Earth and Mars?

Tectonic activity is driven largely by heat inside a planet, which helps move its mantle and crust. Mars is smaller than Earth, so it lost much of its internal heat more quickly and now has weaker geological activity. Thus, “Mars has a thinner crust and weaker internal heat” is the best choice; the key difference is its weaker internal heat.

AI-written and checked against the verified answer.