作主語補足語

帶有賓語補足語的謂語動詞變為被動語態時，賓語成了主語，賓語補足語也就相應地成為主語補足語。當動詞不定式用作主語補足語時，一律要用帶“to”的形式。如：

Their children are allowed to make their own decisions.

允許他們的孩子自己拿主意。

The elephant was made to dance before audience.

使大象在觀眾前跳舞。

不定式結構在英語文章中使用頻率較高, 如下面的這段文字中(4個句子), 不定式結構出現了5次, 請大家確認這些不定式結構在句子中的語能.

（1）So far there is no data to suggest that people living on metal-rich soils experience a potential health hazard. (2) They are also the most likely ones to eat potentially dangerous metal-rich soil. (3) Some trace metals are alleged to cause cancer and also known to cause poisoning中毒. (4) There is a vital need to understand the potential risks and long-term health effects of living on naturally contaminated soils.

提示: 相鄰語句往往圍繞同一中心發展, 在詞語上常常表現為: 相鄰語句中出現呼應的詞語.

分析：第1，2，4句中不定式是作定語；第3句的不定式是作主補；

(hazard –danger 危險)

(hazardous – dangerous危險的)

(contaminate - pollute污染)