英語(yǔ)有個(gè)很有用的結(jié)構(gòu)，就是：疑問(wèn)詞+不定式動(dòng)詞(question word + to-infinitive)。

疑問(wèn)詞是疑問(wèn)代詞“who, whom, what, which, whose”和疑問(wèn)副詞“when, where, how, why ”。此外，連接詞“whether”也適用。

“疑問(wèn)詞+不定式動(dòng)詞”結(jié)構(gòu)有何功用呢?其主要功用有下列五種：

⑴當(dāng)主語(yǔ)，如：

● When to hold the meeting has not yet been decided.

● Where to live is a problem.

● How to cope with the rising cost of living becomes a daily discussion topic.

⑵當(dāng)賓語(yǔ)，如：

● We must know what to say at a meeting.

● He could not tell whom to trust.

● Do you know how to play bridge?

⑶當(dāng)補(bǔ)足語(yǔ)，如：

● The problem is where to find the financial aid.

● The question is who to elect.

⑷當(dāng)名詞同位語(yǔ)，如：

● Tom had no idea which book to read first.

● Do you have a rough impression how to do it?

⑸當(dāng)賓語(yǔ)補(bǔ)足語(yǔ)，如：

● Jim is not sure whose to choose.

● Mary and John are not certain whether to get married or not.

適用于“疑問(wèn)詞+不定式動(dòng)詞”的動(dòng)詞包括：“know, see, decide, tell, ask, consider, discover, explain, forget, guess, hear, imagine, inquire, learn, remember, think, wonder, understand”等。

有點(diǎn)值得特別注意的是：當(dāng)這結(jié)構(gòu)當(dāng)賓語(yǔ)時(shí)，它的作用等于名詞分句，例如：

● I could not decide which dictonary to buy. / I could not decide which dictionary I should buy.

● Jack did not know where to find such a good teacher./ Jack did not know where he could find such a good teacher.

有些動(dòng)詞，如“ask, show, tell, advise, inform, teach”等，可以先有個(gè)賓語(yǔ)，然后才接著加上適當(dāng)?shù)摹耙蓡?wèn)詞+不定式動(dòng)詞” 結(jié)構(gòu)。例如：

● The chief technician showed the apprentice how to repair the machine.

● Have you told him where to get the application form?

綜上所述，可見(jiàn)“疑問(wèn)詞+不定式動(dòng)詞”結(jié)構(gòu)是個(gè)形象清新，既容易用又不容易出錯(cuò)的特別結(jié)構(gòu)，可以多多運(yùn)用。