Which best describes the transition from gas to liquid?
a. energy must be removed because particles in liquid move more slowly.
b. energy must be added because particles in liquid move more quickly.
c. energy is neither added nor removed in this phase transition.
d. energy is either removed or added, depending on the type of particles.

A  Energy must be removed because particles in liquid move more slowly

Explanation:

Gas particles move rapidly colliding with each other, this is as a result of high mobility rate of gases than liquid.  Also gases have higher entropy compared to liquid.

The removal of energy from the gas molecules can reduce the rate of the gas particles collision, thereby leading to its transition to liquid which move at lower rate than gas particles.

Correct option is A "Energy must be removed because particles in liquid move more slowly"

need to see circuit to get time constant