怎样区分及使用被动语态？

我们在平常的英语交流中，尽量使用主动语态，但在下列情况下，则通常使用使用被动语态：

1. 不知道动作的执行者是谁，或没有必要指出动作的执行者时。如：

The glass is broken. 玻璃杯破了。

Letters are collected at eight every morning. 信件每天早晨八点收取。

2. 为了强调或突出动作的承受者时。如：

The desk was made by Master Wang. 这张课桌是王师傅做的。

The bag was taken away by his sister. 那个口袋是她姐姐提走的。

3. 在上下文中，为了使句子间连接紧密时。如：

I have a new motorbike. It was given to me as a birthday present by my father. 我有辆新摩托车。它是父亲送给我作为生日礼物的。

4. 在新闻报道中，为了表明报道的客观性而避免主观性的透露时。如：

A car accident happened on the high way this morning. Three men were killed, the wounded were taken away to hospital at once and policemen were sent there to cope with the event. 今天早晨高速公路上发生了一起车祸，三人丧生，伤员马上被送往了医院，并马上派了警察去处理这一事件(from

5. 在科技论文中，常使用被动语态来强调客观事实。如：

When it is cold enough, water will be turned into ice. 当天气足够冷时，水就会变成冰。

So far, the moon has been visited by earthmen several times. 到目前为止，地球人已经几次拜访了月亮。