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counting and probability senior

Problem

Alice, Bob, and Carol play a game in which each of them chooses a real number between and The winner of the game is the one whose number is between the numbers chosen by the other two players. Alice announces that she will choose her number uniformly at random from all the numbers between and and Bob announces that he will choose his number uniformly at random from all the numbers between and Armed with this information, what number should Carol choose to maximize her chance of winning?
(A)
(B)
(C)
(D)
Solution
The expected value of Alice's number is and the expected value of Bob's number is To maximize her chance of winning, Carol should choose the midpoint between these two expected values. So, the answer is Alternatively, once we recognize that the answer lies in the interval we should choose since no other answer choices lie in this interval.
Final answer
B