Archimedes' Principle Determines Equal Upthrust Steps:

• Both X and Y have identical volumes and are fully submerged, displacing the same volume of liquid.
• Upthrust equals the weight of displaced liquid: upthrust = ρ_liquid × g × V_displaced.
• Since V_displaced is the same, upthrust is identical for X and Y.
• Stationary condition implies holding forces balance the weights, but upthrust remains equal.

Why C is correct:

• Upthrust depends solely on the volume of liquid displaced, which is equal for both objects per Archimedes' principle.

Why the others are wrong:

• A: Force on top surface = pressure at top × top area; depths and areas may differ, so not necessarily greater for X.
• B: Pressure difference = ρ_liquid × g × height; heights may differ despite equal volumes, so not necessarily the same.
• D: Weight = material density × volume × g; Y's density is twice X's with equal volume, so Y's weight is twice X's.

Final answer: C