https://online2.tingclass.net/lesson/shi0529/10000/10243/72.mp3
https://image.tingclass.net/statics/js/2012
本期内容：
doubt is the key to knowledge
怀疑是知识的钥匙
首先我们来学习一个新单词 doubtD-O-U-B-T 怀疑
再来学习一个表达
sth is the key to sth 什么的钥匙 这里注意介词要用to
the key to the car 车的钥匙
the key to my house 我房子的钥匙
doubt is the key to knowledge
怀疑是知识的钥匙
