Read the following SAT test question and then click on a button to select your answer.

A jar contains only red marbles and green marbles. If a marble is selected at random from the jar, the probability that a red marble will be selected is 2/3. If there are 36 green marbles in the jar, how many red marbles are there in the jar?

(A) 18
(B) 24
(C) 54
(D) 72
(E) 108

来源:可可英语 http://www.kekenet.com/sat/201501/356179.shtml