1. 不定式前置

　　1) Derive [A] mineral resources from [B] sedimentary rock [C] is a [D] major modern industrial activity.

　　2) in the matriculation for postgraduate in a short time is realy a hard nut.

　　[A] To make high scores[B] To make low goal[C] To the high scores[D] Make the low goals

　　2. 上述形式一般情况不多见，作为考试的规范英语，如果不定式较长，显得头重脚轻，则可由代词“it”作形式主语(形式主语“it”不能由“that”或“this”等其他代词代替)，而将不定式放到后面

　　It is really a hard nut to get high scores in the matriculation for postgraduate in a short time.

　　3) John admitted that it's always difficult .

　　[A] for him being on time[B] being on time for him

　　[C] for him to be on time[D] on time for him

　　4) It is difficult for me [A] to be concentrating [B] while someone [C] is using [D] a vacuum cleaner.

　　3. 不定式后置的情况不仅限于动词是系动词，也适用于其他动词

　　It took us a great deal of efforts to finish that task.

　　It made him extremely happy to get contact with his family in Taiwan since they separated more than 40 years ago.

　　4. 不定式结构所表示的动作是谁做的，即不定式的逻辑主语，通常可以在特定的上下文中能看出，也可以通过带“for +名词短语”辨出

　　It is quite important for us to read good books during the period of general review(总复习)。

　　It is not difficult for those who study maths well to pass the exam.

　　5. 在某些形容词(如careless，clever，considerate， foolish， good， impolite， kind， naughty， nice， silly， stupid等)作表语时，不定式后可以加of来引导出其逻辑主语

　　It is very kind of you to help me./It is stupid of him to do such a silly thing.

　　间或也可用for + there to be 表示(而且there后面的不定式只能是to be)。

　　It's a great pity for there to be much trouble in the company.