九、考查非谓语动词用作主语的问题

原则上说，动词用作主语，只能是不定式或动名词，不能是分词形式。这类考题命题还往往用动词原形作为干扰项进行考查，同学们做题需引起注意。如：

It’s necessary to be prepared for a job interview; _____the answers ready will be of great help.

A. To have had B. Having had C. Have D. Having

分析：答案选D。动名词短语用作主语。

十、考查“(be +) 过去分词+介词”结构

有一类“be+过去分词+介词”结构，如be interested in, be worried about, be lost in, be dressed in 等，也往往是命题的热点。如：

1. _____ in the mountains for a week, the two students were finally saved by the local police.

A. Having lost B. Lost C. Being lost D. Losing

分析：答案选 B。因表示“迷路于”是lose oneself in，题中没有oneself, 所以the two students与lose是被动关系，应该用过去分词作状语。

2. _____ in a white uniform, he looks more like a cook than a doctor.

A. Dressed B. To dress C. Dressing D. Having dressed

分析：答案选 A。由dress的宾语一定是人或oneself可知，dress与he是动宾关系，即he与dress是被动关系，要用过去分词作状语，Dressed in …=As he is dressed in …