过去分词的肯定式与否定式
1. 过去分词的肯定式就是过去分词的基本式。如：
He felt himself compelled to bring this action. 他感到自己被迫进行这次诉讼。
We’ll have to get the car repaired before Tuesday. 我们必须在星期二以前把汽车修好。
She had to shout to make herself heard. 她必须大声喊才能让人听见她说话。
Looked at politically, it is an important problem. 从政治上看这是一个重要问题。
No photographer is allowed to shoot the president’s crippled walk. 不许任何摄影记者对总统的跛行拍照。
The excited children are opening their Christmas presents. 激动的孩子们正在把圣诞礼物打开。
Taken in small doses, this drug is completely harmless. 小剂量服用这种药是完全无害的。
Beaten by the police, sent to jail, Gandhi invented the principle of nonviolent resistance. 尽管受警察的殴打，被投入监牢，甘地却首创了非暴力抵抗的原则。
2. 过去分词的否定式是在过去分词的前面加上否定词not。如：
Everyone helped, John not excepted. 大家都来帮忙，约翰也不例外。
Not given enough time, he couldn’t finish the job on time. 因为没有给他足够的时间，所以他没能按时完成工作。
Not replaced by any other energy, oil is likely to be used up in the nearest future. 由于还没其他任何能源可代替，石油很可能在不久的将来被使用殆尽。