重点讲解：
1. be known as 称为；叫做；认为；
例句：The violin is known as the queen of instruments.
小提琴有乐器皇后之称。
2. cut down 砍倒（树木）；
例句：A vandal with a chainsaw cut down a tree.
一个故意破坏公物的人用链锯伐倒了一棵树。
3. pass down 使流传；
例句：Folk music has been passed down from one generation to another.
民间音乐是一代一代流传下来的。
4. for sure 无疑;肯定；
例句：Nobody knows the cause of the fire for sure.
没有人确切地知道大火的原因。
5. at the most 至多；最多；
例句：It will take two hours at the most to get there.
最多两小时便可到达那里。
