The masses cannot be compared without a balance. The mass of the feathers is less than the mass of the nails. The mass of the feathers is the same as the mass of the nails. The mass of the feathers is greater than the mass of the nails.
I gave my students this multiple choice question: A student has one liter of feathers and one liter of iron nails. Which statement best compares the masses of the two samples?

Only one answer is correct among these 4 choices:
- The masses cannot be compared without a balance.
- The mass of the feathers is less than the mass of the nails.
- The mass of the feathers is the same as the mass of the nails.
- The mass of the feathers is greater than the mass of the nails.

Could you tell me which one is correct?

The mass of the feathers is less than the mass of the nails.