Galileo discovered four moons in orbit about Jupiter; this suggested that

• A. bodies could stay in orbit about a moving Jupiter.
• B. Jupiter is the smallest planet.
• C. Moons orbit the Sun.
• D. Earth is at the center.

Answer: (A)

Orbital motion can occur around a moving primary. Galileo’s observation that four moons orbit Jupiter demonstrates that a planet, even while it itself is moving through space, can have objects bound to it by gravity and stay in orbit. This provides evidence against the idea that all bodies must orbit Earth or a stationary Sun and supports the broader view that planetary systems can include satellites orbiting a moving planet.

Why the other ideas don’t fit: discovering moons around Jupiter doesn’t imply that Jupiter is the smallest planet; in fact, Jupiter is much larger than Earth and the moons themselves. The moons Galileo found orbit Jupiter, not the Sun, so it doesn’t support “moons orbit the Sun.” And this finding challenges an Earth-centered view rather than supporting Earth at the center.