It is said that a smile sends a positive message and is appropriate in all but a life and death situation.
非人称转述结构
一、定义
转述人们的一般认识或说的话时，我们可以用It + 动词 (如：say, know, believe, claim, suppose, think, fear, predict)被动式结构，此种结构被称为“非人称转述结构(Impersonal Report Structure)。
二、用法
It is said that dolphins are very friendly animals.据说海豚是非常友好的动物。
It is reported that the plane was hijacked.据报道飞机被劫持了。
上述结构也可转换为另外一种结构，可以把有关的人和事放在句首：subject + the passive + infinitive。
1、如果转述的动作或状态发生于转述的同一时间或还未发生，不定式用一般时。
Dolphins are said to be very friendly animals. 据说海豚是非常友好的动物。
They were feared to give up.他们恐怕会放弃。
2、如果转述的动作发生在转述之前，不定式用完成时。
The plane is reported to have been hijacked. 据报道飞机被劫持了。
3、如果转述的动作正在发生，不定式用进行时。
He is said to be studying abroad now.据说他现在正在国外学习。
