Passage Summary: Mars has a volcano the size of a small country, but Earth's surface is too flimsy to hold something that heavy without sinking, regardless of gravity.

Reasoning: Mars has a massive volcano that Earth's crust could not support; even if gravity were equalized, Earth's crust is too thin and would buckle under such weight.

Analysis: Since this is a 'Must be True' question, we need to find a statement that is strictly supported by the comparison between the two planets. The stimulus explicitly states that Earth's crust would buckle under a mass that Mars's crust is currently supporting. This implies a direct physical difference between the two: Mars's crust must be thicker or structurally stronger than Earth's crust. Look for an answer that focuses on the relative strength or thickness of the planetary crusts rather than the volcanoes themselves.