The gravitational potential energy of a contracting interstellar cloud

a. stays the same at all times.

b. gradually transforms into other forms of energy.

c. gradually grows larger.

d. could grow larger or smaller, depending the cloud's rotation.

b) gradually transforms into other forms of energy.

Explanation:

Interstellar clouds are composed of gases, plasma and dust etc. So when the gravitation force becomes stronger the clouds starts to contract which results in the reduction of the gravitational potential energy. As the gravitational potential energy decreases, there is an increase in the kinetic energy in the form of heat and temperature. Thats why we say that upon contraction of the interstellar clouds the gravitational potential energy gradually transforms into other forms of energy.