并不是所有的形容词后要用虚拟语气.常用的：important,necessary,urgent,essential,vital,natural,strange,proper等
It is necessary that the program (should) be loaded into the computer.有必要把程序输入电脑.
It is strange that he should have learned so much in such a short time.很奇怪他竟然在如此短的时间内学了那么多的东西.
It is desired that we (should) get everything ready by tonight.希望一切在今晚前准备就绪.