As an interstellar gas cloud shrinks in size, its gravitational potential energy:
a) stays the same at all times.
b) gradually is transformed into other forms of energy.
c) gradually grows larger.

b) gradually is transformed into other forms of energy.

Explanation:

According to the virial theorem, the gravitational potential energy of the the gas cloud is converted into two forms of energy. The collapse provides enough kinetic energy to the particles for hydrogen fusion to occur. Due to the collisions between particles the cloud will heat up. The other part of the gravitational potential energy is released through radiation due to the nuclear fusion.

in simple terms, the principle states that the buoyancy force on an object is equal to the weight of the fluid displaced by the object, or the density of the fluid multiplied by the submerged volume times the gravitational acceleration, g. this is also known as upthrust.

answer: the exterior temperature of commercial jet planes as they leave the stratosphere and return to the ground increases steadily.

explanation:

the lower most layer of atmosphere is troposphere which extends from 0 to 12 km above the surface of the earth. the temperature initially decreases as distance is increased from the earth's surface. commercial jets fly in lower part of the stratosphere. the stratosphere extends upto 50 km. the temperature in stratosphere starts rising again due to presence of ozone which traps the uv rays.

thus, when the planes leave the stratosphere and return to the ground, the exterior temperature increases steadily.