【问】...it would be unforgivable to miss it(=the train). (New Concept English，Book 3，L.60) 这里为什么要用虚拟语气would be? 【答】 充当主语的动词不定式有时表示真实的情况，有时则表示假设的或可能发生的情况。在后两种场合下，谓语动词要采用虚拟语气。例如： 1. The molecules of water are incredibly minute，It would take about 125 million of them toform a row an inch long. 水分子小得难以置信。把水分子排成一英寸长就需要大约一亿二千五百万个分子。 (动词不定式短语所表达的事情是假想的，不是真的要去做的) 2. ...it would perhaps be unwise to forecast undue restrictions on the nature of the ultimateachievement. ……现在便对其最终成果的性质预先定下不适当的框框，也许是不明智的。 3. It would be impossible to estimate how many crimes went undetected last year. 要想估计出去年有多少犯罪活动未被发现，那是不可能的。 4. It would be a shame to stay indoors on such a beautiful day. (Chambers) 这样美好的时光，要是呆在家里，那就太可惜了。 请做下面的英语试题： 1. “Tell the nurse you've been waiting an hour. ” “Not now. She's talking to a patient，and _______. ” A. it would be rude interruption B. interruption would be rude of me C. if I interrupt would be rude D. it would be rude to interrupt(TOEFL，73.6) 2. It would be________ a risk to let the child go to school by himself. A. following B. passing C. running D. carrying (Nelson，500B) (参见subjunctive mood9B项)