Weight difference equals mass times gravitational field difference

Steps:

• Weight on Earth = mass × 9.8 N/kg
• Weight on Mars = mass × 3.7 N/kg
• Difference in weight = mass × (9.8 - 3.7) = mass × 6.1 N/kg = 25 N
• Mass = 25 / 6.1 ≈ 4.1 kg

Why C is correct:

• 4.1 kg yields exactly 25 N difference using the formula Δweight = m × Δg, where Δg = 6.1 N/kg.

Why the others are wrong:

• A: 1.9 kg gives 11.6 N difference, too low.
• B: 2.8 kg gives 17.1 N difference, too low.
• D: 6.8 kg gives 41.5 N difference, too high.

Final answer: C