7.The most common use of telecommunication satellites，however，has been for transmitting telephone calls.however
    在本句中做副詞用，意思相當(dāng)于but.但是however和but在用法上是有差異的。however不放在句首或句末時(shí)，前后通常都加逗號(hào)，而but則不用。請(qǐng)看例句：
    1）It is not，however， the only answer to the question. （然而，這不是問題的答案。）
    2）I'd like to go and see the films，however，I don't have the time. （我很想去看電影，但我沒時(shí)間。）
    3）However，we still have 10minutes left. （不過，我們還有十分鐘。）
    4）The composition is well written， there is room for improvement， however.
    5）I am sorry，but I won't be able to come this time. （很報(bào)歉，我這次不能來了。）
    6）He would like to go， but he was busy. （他想去，但他太忙。）
    7）It's not cheap， but it's really good. （這個(gè)不便宜，但的確很好。）
    8. Telecommunication can make information from around the world available to use quickly and easily， but some people worry that this may be a risk to our privacy.
    available是一個(gè)形容詞，意思是“可得到的；可用的；有效的”。
    1）I am sorry those shoes are not available in your size. （很報(bào)歉，那些鞋沒你的尺碼。）
    2）If I am not available when you call， leave a message. （你打電話來時(shí)如果我不在，請(qǐng)留個(gè)言。）
    3）If the tickets is available， I will go to the concert. （如果能弄到票，我會(huì)去聽音樂會(huì)。）
    4）The ticket is available on the day of issue only. （此票僅發(fā)售當(dāng)天有效。）
    9.We can prevent this from happening by carefully controlling the new technology.
    prevent…from…意思為“阻止…發(fā)生”，也可用stop…from…或keep…from.From可被省去。例如：
    1）They tried every means to prevent the disease （from） spreading. （他們想方設(shè)法阻止疾病曼延。）
    2）Nothing can prevent him （from） going there.（什么也阻止不了他去那兒。）
    本課主要詞組及語法要點(diǎn)
    詞組：
    1. at the beginning of 2.means of
    3. over long distance 4. by the middle of
    5. such as 6. change into
    7. from…to… 8. be capable of
    9. not only…but… 10.in theory
    11. have access to 12.amount of
    13. provide…to… 14.follow sb's instructions
    15. care for 16. as well as
    17. at the same time 18. make…available
    19. pay for 20.isolate…from…
    語法：
    1.過去完成時(shí)
    1）…both radio and television had be come established means of transmitting sounds and pictures.
    2. 非限定性定語從句
    1）…radio waves， which are then sent from a station on earth to an orbiting satellite.
    2）…back to earth， where another station picks them up and changes them back into television signals.
    3）The combination of satellites，which transmit information，computers，which store information，and television，which displays information，will change every home into an education and entertainment center.
    2. 賓語從句
    1）We must remember that technology alone is not the answer.
    2）The satellite also demonstrated how it could provide help to people living in isolated areas…。
    3. 注意such as，as well as，as的用法
    1）In order to transmit an event such as the Olympics via satellite， …
    2）…printed materials such as books and magazines.
    3）…as well as get any information they need， …
    4）As one telecommunication expert days， …
    Text B What People Don't Know about Air
    短語表達(dá)
    1. without
    We couldn't have finished the work so soon without your help.
    Without air，there would be no wind or clouds.
    2. adv. + past participle
    It is widely known that the earth goes around the sun.
    It is generally believed that the earth is getting hotter.
    3. where
    Where there is a will，there is a way.
    Where there is hope，there is life.
    4. be forced to
    He was forced to drop out of school.
    They were forced to work 14 hours a day.
    5. shelter v.& n.
    Mother tried to shelter her from the blow of the tragic news.
    You have to find shelter from the blazing sun.
    6. protect from
    It is necessary that we protect our skin from being burned by the sun.
    She had his umbrella to protect her from the sun.
    7. deadly adj.
    They made a deadly attack on the enemy's air base.
    A drop of this poison might be deadly to man.
    8. burst
    As he braked a tire burst.
    All the boys burst from their tents.
    Everybody in the room burst out laughing.
    The little girl burst into tears.
    9. rest upon
    His arm rested upon the table.
    The task rested upon my shoulder.
    His eyes rested upon a strange object.
    10. gaze at
    He was standing at the window， gazing at the street.
    What are you gazing at？
    11. not…until
    He didn't go out to play until he finished his homework.
    No one was to go to bed until further order.
    12. in the meantime
    His case won't come to court for several months， and in the meantime more than half of the people think him guilty.
    At last we were released. In the meantime， our friend had informed the newspaper.
    13. pay attention to
    Please pay more attention to your spelling next time.
    I didn't pay much attention to what he said yesterday.
    14. add to
    If you praise others more often， you can add great happiness to their life.
    What he said just now added to my confusion.