题目

I was told that the singer ________ in 1980. A . was born B . is born C . had been born D . had born 答案：A一个不透明的口袋中，装有红球6个，白球9个，黑球3个，这些球除颜色不同外没有任何区别，现从中任意摸出一个球，恰好是黑球的概率为________．