重点讲解：
1. prior to 在…之前；先于；
It happened prior to his arrival.
这事发生在他到达以前。
2. be subject to 受…支配的；服从于…的；
This is subject to your approval.
请你审批。
3. a total of 总数；总共；
The project which began in 2007 is supposed to cost a total of 8,000,000,000 dollars.
这项工程从2007年开始，预计总共花费80亿美元。
4. be known as 称为；叫做；
She was known as the "Iron Lady".
大家都称她为“铁娘子”。