重点讲解：
1. know of 听说过；略有耳闻；
I know of him, but I can't really say that I know him.
我只是听说过他，但是我不能说我认识他G%JX!8&|X@VNMnvB.。
2. all over 到处；遍及；
We have friends all over the world.
我们的朋友遍天下2pup6+~3yRz8。
3. tell apart 区分；区别；辨别；
Free range and battery eggs, boiled for four minutes, were hard to tell apart.
柴鸡蛋和笼养鸡蛋在煮过4分钟之后很难区分Gq6^^-(5[N.。
4. be vulnerable to 易受伤害的；易受影响的；
Tourists are more vulnerable to attack, because they do not know which areas of the city to avoid.
游客们最容易受到袭击，因为他们不知道应该不去城市里哪些地区d&)CvF09^U。