Which statement is true of all matter?
A. It has mass
B. It can be seen
C. It exists only as a solid.
D. It maintains its shape and size.
My mind is blank, and I can't seem to remember. ._.
Air is matter, and can't be seen thus not all matter can be seen. Any liquid or gaseous is matter (water, air, etc.) Since it can be liquid or gaseous it doesn't have to maintain it's shape and size to be matter.
