be to do 具有八種用法：表達堅決的命令、指示“計劃”或“安排的事項”、表明“可能性”、體現“意圖”、表示“應該”、傳達“注定”“不可避免”“必然發生”的意義、在虛擬語氣中表示一種假設,以及蘊含“期待將來”的含義。

1. 表達堅決的命令,意為“必須”。

(1) This naughty boy is to stay here until the class is over. 這個頑皮的男孩必須待到下課。

(2) No one is to enter this building without the permission of the security guard. 未經保安許可,任何人不得進入此樓。

2. 指示“計劃”或“安排的事項”。

(1) Betty is to be married soon. 貝蒂即將步入婚姻殿堂。

(2) An insurance agent is to meet us this afternoon. 今天下午,我們將與一位保險代理人會面。

3. 表明“可能性”。

(1) Are you to pay the debt for your wife? 你會為你的妻子償還債務嗎？

(2) The lovely puppy is nowhere to be found. 那只可愛的小狗無影無蹤。

4. 體現“意圖”“決心”或“打算”。

(1) If you are to be there on time, you had better hurry. 若想準時到達,你最好加快速度。

(2) If all of us are to remain friendly, we must be sincere with one another. 若想保持友好關系,我們必須彼此真誠。

5. 表示“應該”。

(1) You have done so well. You are to be rewarded. 你表現出色,理應得到獎勵。

(2) Such nasty questions are to be avoided. 你應避免提出如此惡劣的問題。

(3) You are to call the police. 你應該報警。

6. 傳達“注定”“不可避免”“必然會發生”的意義。

(1) Anne was wondering what was to become of her boyfriend, Tommy. 安妮擔憂她的男友湯米的未來。

(2) The murderer was sentenced to life imprisonment and was never to see his family again. 兇手被判終身監禁,永遠不得與家人相見。

(3) She did not think too much of her unkind acts. However, they were to be harmful to herself, too. 她未深思自己不友善的行為,然而,這些行為終將對她自己不利。

(4) Tom wasn’t worried about his head injury, but it was to be troublesome for him later. 湯姆對頭部的傷勢毫不擔憂,但這傷勢日后必將給他帶來麻煩。

(5) You are to answer for what you have done. 你必將為自己的行為負責。

7. 在虛擬語氣中表示一種假設。

(1) If I were to do it, I would do it well. 若由我來做,我定能做好。

(2) Even if you were to take a taxi now, you would not be able to arrive at your destination on time. 即使你現在乘出租車,也無法準時到達目的地。

8. 蘊含“期待將來”的意思。

(1) The actual usefulness of the newly invented equipment is still to be determined. 這種新發明設備的實際效用尚待觀察。

(2) Henry's appointment with the accountancy firm is yet to be confirmed. 亨利與會計事務所的約會尚待確認。