例句：
This will be a problem for some time to come.
這將是未來一段時期里的一個問題。
This is the one major drawback of the new system.
這是新系統的一大弊端。
This is one of the most commonly used methods.
這是最常采用的方法之一。
It's about this high.
大約有這么高。
The number of new students decreased from 210 to 160 this year.
今年新生人數從210減少到160。