问题补充：
There are so many books!It is not easy for us to decide what to take and what to.
A. take on
B. pick up
C. leave behind
D. work out
答案：
A. take on
B. pick up
(答案→)C. leave behind
D. work out
解析：句意为：有那么多书，很难决定如何取舍。take on表现，展现；pick up拣起，拾起；leave behind未能或忘记带某人某物,留下……；work out解决,回答出。
