酸碱中和滴定实验步骤:非谓语动词的体

非谓语动词中分词的体有完成体和进行体，即having done, having been done和being done，完成体只用于做状语的场合，而进行体可以用于做定语和做补足语。
动名词的体也有having done, having been done和 being done的结构主要用于做主语和宾语的场合。
不定式的体有to be doing 和to have done，主要用于pretend, happen, seem, appear, be said to等结构中。如：
① The man in the corner confessed to _____ a lie to the manager of the company.(1997.6)
A. have told B. be told C. being told D. having told
having told在句中做介词宾语，表示动作发生在谓语动词之前。

② I'd rather read than watch television; the programs seem ____ all the time.(1997.1)
A. to get worse B. to be getting worse C. to have got worse D. getting worse
从all the time的使用可以推断get worse是一个渐变过程，所以用不定式的进行体。

③ The speech _____ a lively discussion started.(1995.1)
A. being delivered B. was delivered C. be delivered D. having been delivered
该结构属于独立主格结构做时间状语，状语分词所表示的动作发生在谓语动词之前，所以应该用完成体，答案为D。