重点讲解:
1. at least 至少
I spend at least six hours a week marking.
我每周至少要花六个小时批改作业
。2. be able to do sth. 有能力做某事
I haven't been able to get much work done today.
我今天未能干多少工作
。3. date back to 追溯到;从...开始
The tradition could date back to 300 BC.
这一传统可追溯到公元前300年
。4. around the world 世界各地
He bummed around the world for a year.
他在世界各地漫游了一年
。