Density inversely proportional to volume for constant mass

Steps:

• Mass of air remains constant as it's trapped in a closed cylinder.
• Density equals mass divided by volume.
• Piston movement reduces volume (assumed halved based on options).
• Final density = initial density × (initial volume / final volume) = 0.012 g/cm³ × 2 = 0.024 g/cm³.

Why C is correct:

• Doubling density follows the inverse relationship from Boyle's law and mass conservation when volume halves.

Why the others are wrong:

• A halves density, which occurs if volume doubled.
• B keeps density same, ignoring volume change.
• D quadruples density, which requires volume quartered.

Final answer: C