6. wish的用法
1）wish后面的从句，表示与事实相反的情况，或表示将来不太可能实现的愿望。其宾语从句的动词形式为：
a. 从句动作先于主句动词动作（be的过去式为 were）
主句：现在时
从句：过去时
b. 从句动作与主句动作同时发生（had + 过去分词）
主句：过去时
从句：过去完成时
c. 将来不大可能实现的愿望
主句：将来时
从句：would/could +动词原形
例如：
I wish I were as tall as you.　我希望和你一样高。
He wished he hadn't said that. 他希望他没讲过那样的话。
I wish it would rain tomorrow. 我希望明天下雨就好了。
2）wish to do；wish sb / sth to do。
例如：
I wish to see the manager. = I want to see the manager. 我希望见一见经理。
I wish the manager to be informed at once. （= I want the manager to be informed at once.）我希望经理能马上得到消息。

7. 比较if only与only if
only if表示"只有"；if only则表示"如果……就好了"。If only也可用于陈述语气。例如：
I wake up only if the alarm clock rings. 只有闹钟响了，我才会醒。
If only the alarm clock had rung. 当时闹钟响就好了。
If only he comes early. 但愿他早点回来。

8. It is（high）time that
It is（high）time that 后面的从句谓语动词要用过去式或用should加动词原形，但should不可省略。例如：
It is time that the children went to bed. 孩子们该睡觉了。
It is high time that the children should go to bed.

9. need "不必做"和"本不必做"
1) didn't need to do表示过去不必做某事, 事实上也没做。
2) needn't have done表示过去不必做某事, 但事实上做了。
例如：
John went to the station with the car to meet Mary, so she didn't need to walk back home.
约翰开车去车站接玛丽，所以她不必步行回家了。
John went to the station with the car to meet Mary, so she needn't have walked back home.
约翰开车去车站接玛丽，所以她本不必步行回家了。（Mary步行回家了，没有遇上John的车。）
典型例题：
There was plenty of time. She ___.
A. mustn't have hurried　 B. couldn't have hurried　　C. must not hurry　 D. needn't have hurried
答案D。needn't have done. 意为"本不必"，即已经做了某事，而时实际上不必要。
mustn't have done 用法不正确，对过去发生的事情进行否定性推断应为couldn't have done, "不可能已经"。 must not do 不可以（用于一般现在时）。