A box contains 3 yellow balls and 6 black balls. One by one, every ball is selected at random without replacement. What is the probability that the fourth ball selected is black?
Choose the correct answer:
A) 4/7
B) 3/5
C) 5/8
D) 2/3
E) 3/4
Each ball has an equal chance (1/9) of being selected fourth.   The probability that a black ball is selected fourth is 6/9 = 2/3.   The answer is 2/3.
<result>D</result>
A box contains 3 yellow balls and 6 black balls. One by one, every ball is selected at random without replacement. What is the probability that the fourth ball selected is black?