Task: Question Answering
Input (English): A bag contains two white marbles, four blue marbles, and an unknown number of black marbles. When one marble is drawn from the bag at random, the probability that the marble is black will be \(\frac { 1 } { 3 } \). How many black marbles are in the bag?
(A)3 (B)4 (C)5 (D)6 (E)8
Output (English): A