There are 10 books on a shelf, of which 4 are paperbacks and 6 are hardbacks. How many possible selections of 5 books from the shelf contain at least one paperback and at least one hardback?

A、75
B、120
C、210
D、246
E、252

答案：D

专业教师答疑

问题：为什么c（4，1）c（6，1）c（8，3）取出来的是不完整的查看答疑

问题：请问数学老师，为什么不是绿色笔写的那种。我四本paperback选一本，六本hardbacks选一本，接下来我随便选嘛。

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