有問必答

李順發

It， that， one用法相比較，有哪些異同？

答：1. it和that都可用來代替物質名詞和抽象名詞，而one則不能。這時it指同一事物，而that只能指同類事物。如：

①There is air all around us， though we cant see it.

②His attitude to us is that of a comrade.

③Your question is one of great importance.

以上句①it替代同一air。句②that替代attitude.His attitude與the attitude of a comrade是同一類的。句③one替代可數名詞question.

2. it， that， one都可用于代替可數名詞。that和one只是代表上文提到的某一個名詞，不一定代表同一事物。其中one表示泛指，代替a/an+名詞（可數名詞）；that表示特指，代替the+名詞；it也表示特指，但它代表上文提到的名詞時，是指同一個事物。

①—Do you need my pencil ？

—No， thanks. I have got one myself.

②—Where is my book？

—I have lost it.

句①中的one不是上句提到的“我的pencil”，而是另外一支，表示泛指；句②中的it就是指上句提到的“我的那本書”。

3. one前面可以有冠詞、代詞、形容詞修飾，后面可以有介詞短語、定語從句修飾，而it和that前面則不能。one的復數形式為ones.

I dont want a new car. I want a second-hand one.

The book is one about English study.

Our era is one in which a great number of heroes emerge.

—Which book would you like—this one or that one？

—Either one is fine.

Here are two pens. Which one do you prefer ？

—This is very beautiful.

—Yes， at least it is no worse than the one I bought last week.

Modern farms are larger than old-time ones.

In Britain the villages are becoming small towns and the small towns large ones.

4. it和that可用來代替前面整個句子的意思，而one則不能。

I would like to give him a hand. It is my duty.

During the next ten years we both worked night and day. That is why you see this old woman before you now.

5. 在比較狀語從句中，一般用that代替不可數名詞。若是特指的單數可數名詞，用that one；若是特指的復數名詞，則用those代替。

The population of China is much larger than that of Japan.

No bread eaten by man is so sweet as that earned by his own labour.

We like this computer better than that one.

The people in this place are more hardworking than those in that place.

“be+to do”結構有哪些用法？

答：1. 表示按計劃或安排將要做的事情。如：

The train for Wuhan is to start at 10：20. 去武漢的火車10點20分開。

We are to begin the work next month. 我們計劃下個月開始這項工作

She is to be seen in the lab on Monday. 星期一你準會在實驗室見到她。

這一結構也可用于表示過去曾經計劃要做的事。如果這種事沒有發生，可以用動詞不定式的完成式。如：

She was to have summer holidays in Dalian last year. 去年她曾打算去大連度暑假。

I was to have started work last week， but I changed my mind. 我本該上星期開始工作，但我改變了主意。

2. 表示命令指示。如：

Mother says you are to wait here till she comes. 媽媽要你在這兒一直等到她來。

You are not to smoke. 不準吸煙。

The room is to be locked. 這房間要上鎖。