Why can gasses change volume? A. The forces holding the gas particles together are
stronger than gravity.
B. The gas particles have no mass, so they can change volume.
C. Gravity has no effect on gas particles, so they can float away.
O D. There are no forces holding the gas particles together.

I think it is b because

The molecules in a gas are very far apart compared with the molecules in a solid or a liquid. The amount of space between the molecules in a gas can change easily. If a rigid container—one that cannot change its shape—has a certain amount of air and more air is pumped in, the volume of the gas does not change.

B. a graduated substance