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。
Researchers in this field have made some important new discoveries.
这个领域的研究人员有了一些重大的新发现。
Teachers are up against some major problems these days.
老师们最近面临着一些重大问题。
Digital television has been around for some time now.
数字电视已经面市一段时间了。