制作统计表，线条不宜过多，但必要时也可以有竖线及斜线。
参考答案：错
外贸单证有哪些种类
—What do you think we can do for our aged parents?
—You __ ___ do anything except to be with them and be yourself.[ ]
A. don’t have to
B. oughtn’t to
C. mustn’t
D. can’t
