例句：
1、We go there maybe once or twice a month.
我們每月大概去那里一到兩次。
2、You should visit your dentist at least twice a year.
你應該每年至少去看兩次牙科醫生。
3、New drivers have twice as many accidents as experienced drivers.
新駕駛員所出的事故是老駕駛員的兩倍。
4、You should think twice about employing someone you've never met.
雇用素不相識的人應三思而行。