[問題]GWD23-30

[magic]

Q30:
There are 8 books on a shelf, of which 2 are paperbacks and 6 are hardbacks. How many possible selections of 4 books from this self include at least one paperback?

A. 40
B. 45
C. 50
D. 55
E. 60
答案是C
可是我怎麼算都是D耶
可以指點一下嗎
謝謝