题目

—Aren't the elephants from Thailand?— A . Yes, they are. B . Yes, they aren't. C . No, they are. D . No, they don't. 答案：A在一个口袋中装有个白球和个黑球，这些球除颜色外完全相同，从中摸出个球，至少    摸到个黑球的概率等于  (      )    (A)             (B)              (C)               (D)