Galileo's Equivalence Principle in Vacuum

Steps:

• Acceleration due to gravity on the Moon is g_moon, constant for all masses.
• No atmosphere means no drag force affecting motion.
• Both spheres start from rest at identical height h.
• Fall time t = sqrt(2h/g_moon) is mass-independent, so they reach ground simultaneously.

Why D is correct:

• Newton's second law (F = mg) yields a = g_moon for both, per equivalence principle.

Why the others are wrong:

• A: Acceleration is identical, not smaller for larger mass.
• B: Both hit simultaneously, so no "first."
• C: Acceleration is identical, not smaller for smaller mass.

Final answer: D