例句：
This will be a problem for some time to come.
这将是未来一段时期里的一个问题。
This is the one major drawback of the new system.
这是新系统的`一大弊端。
This is one of the most commonly used methods.
这是最常采用的方法之一。
It's about this high.
大约有这么高。
The number of new students decreased from 210 to 160 this year.
今年新生人数从210减少到160。