选择题
2016 AMC 8 Problem 21: Red Chips First
A top hat contains 3 red chips and 2 green chips. Chips are drawn randomly, one at a time without replacement, until all 3 of the reds are drawn or until both green chips are drawn. What is the probability that the 3 reds are drawn?
2016 AMC 8 第 21 题：红筹优先
高顶帽子包含 3 个红色筹码和 2 个绿色筹码。筹码是随机抽出的，一次一个，无需更换，直到抽出所有 3 个红色筹码或抽出两个绿色筹码。抽出 3 个红色的概率是多少
A.
3/10
B.
2/5
C.
1/2
D.
3/5
E.
7/10