A container holds gas molecules of mass m at a temperature T. A small probe inserted into the container measures the value of the x component of the velocity of the molecules. What is the average value of 1 half m v subscript x squared for these molecules?

(a) (3/2)kT

(b) (1/2) kT

(c) kT

(d) square root of 3k T

I thought the answer was a.) and I even got a second opinion that it was, but the answer is wrong according to the quiz.