it, one 和 that一向是一个备考的热点问题,前些年的试卷中经常出现,不过现在好像很少见到了。it, 只能是特指上文已经提到过的事物,或是双方都清楚的事物。如 Look at that car, I bought it last week.它还有许多其他的用法,如表示说话人所指的某一种形势或情况。If a fire breaks out in this market, it may cause a lot of deaths.或是说话人所指的某一种情况如,I hate it when people talk with their mouthes full.它还可以用来表示身份或性别不详之人,如 Somebody's knoc...