4．We have had a few songs in the ten, but we really hope to a number one hit some day.

　　 我们已经有几首歌上排行榜了，希望有一天能有一首列入榜首。(参考译文。)

3．must 和have to的区别：

have to是“不得不”，表示客观上的意义；而must是“必须”，表示主观愿望，如：

It’s time for the meeting. I have to go now. 开会的时间到了，我得走了。

否定句,助动词do + not +have

You don’t have to go.你现在不必走。

You must be there on time.你务必按时到达那里。

否定句, 直接+not

You mustn’t go there now. 现在你千万别上那儿去。

must 的否定回答needn’t

Must I go now? 我现在就得走吗？

Yes, you must. 是的，你必须走。

No, you needn’t. 不，不必。

2．He has worked here since 1998. 他从1998年一直在这里工作。

　 此句说明工作这一动作从1998 年持续至今。

He started to work here in1998. 他1998 年开始在这里工作。

虽然现在完成时的动作和一般过去时一样都发生在过去，但它强调的是动作对现在的影响。而一般过去时强调的是动作发生在过去的某一具体时间。

现在我们再注意一下since 和for的用法：

for的后面接一段时间：

I have lived in Beijing for about 12 years. 我在北京已经生活了大约12年了。

since后面接点时间：

I have lived in Beijing since 1994. 我从1994年就一直住在北京 。

同学们从以上两个句子中可以看出其实它们是不同的方式表达了同一个意思。值得注意的是这两个句子动词必须是持续性动词。如：

He has already borrowed that book. 他已经买了那本书。

He has had it for two weeks.他买那本书已经有两周的时间了。

1．Have you packed the beach towels yet? 你把沙滩巾打包进去了吗？

　　 大家知道此句用的是现在完成时。副词yet常用于现在完成时的疑问句和否定句中，而在肯定句中则用already,如：

　 I have already packed the beach towels. 我已经把沙滩巾打包进去了。

　 除此之外just, ever, never等词也常常用在现在完成时态的句子中。

This evening you will enjoy some short plays, songs, dancing and so on by our classmates.

I hope you will like these programs and have a good time.

Thank you.

5. They all help us to know what is going on in the world and what other people are thinking about.

4. Books, magazines, TVs, radios and films all help us to communicate with others.

3. Yes, they can.

2. Signs on the door tell us where to go in or out.

10. has changed a lot