单词释义：根据英语解释写出相对应的单词。

1. a lift in a building _______

2. a word for petrol in American English _______

3. as a matter of fact; in fact _______

4. a set of rooms for living in, usually on one floor of a large building _______

5. all the words that a person knows _______

6. happening often _______

7. accept that something is true or important _______

8. not suddenly _______

9. a way of saying words that shows what place someone comes from _______

10. a big piece or an area of buildings in a town or a city with streets on all four sides _______

服务器系统年停机时间为8.5小时，系统可用性可以达到______。

A．99%
B．99.9%
C．99.99%
D．99.999%