A vapour is said to be saturated when

A.

more molecules return to the liquid than the amount that left it

B.

a dynamic equilibrium exists between the molecules of the liquid and the vapour molecules at a given temperature

C.

the vapour pressure is equal to the atmospheric pressure

D.

all molecules are moving with the same speed in all directions at a given temperature

Correct answer is B

No explanation has been provided for this answer.