An object's motion changes
A. when there are no forces acting upon it.
B. only when a nonzero net force is applied to the object.
C. when the forces acting on the object remain balanced.
D. only if the object is at rest when a force acts upon it.

b

Explanation:

because the nonzero force creates a unbalanced force

B. Only when nonzero net force is applied to the object.

Explanation:

I got this question correct in Study Island :)

Because liquids flow freely, they take the shape of the container they are in, but have a definite volume. Like liquids, the shape of a gas changes with the container. This is because the atoms in a gas move rapidly and freely to fill any available space. Unlike liquids, the volume of a gas changes depending on the container it is in.

Hoped that help :)