Difference between relaxation time and collision time?

Explanation:

Collision time is the average time that is required for a moving individual particle to change direction as a result of collision with particles of type.

Relaxation time is the time required for the amplitude of  an oscillating variable to drop from an initial value to 0.368 of that value. The average resultant velocity drops exponentially to zero in the absence of an electric field.

a. carbon monoxide from car exhaust

b.particulate matter, such as soot

c.water vapor from a factory smokestack

d.acid rain

these are the answer choices im on that question right now