8. It’s a bit difficult to see, especially in the third image, but all the particles are in fact in constant motion. Even in a solid, its particles are constantly moving in place about their axes. So, the answer would be B.
9. Of the choices here, a gas has only a definite mass, but it doesn’t have a definite shape or volume; a gas will take the shape and volume of its container. So, the answer here would be A.
10. This is a trick question unless you can pick more than one answer. Particles in both a liquid and a gas are not fixed in place and can move from one place to another. So, the correct answer(s) can be either or both B and C.
10. A change in either pressure or temperature can affect the space between gas particles, i.e., the gas’s volume. So, the correct answer here would be C.