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阅读短文并回答。超声波及其应用

人能够听到声音的频率范围从20HZ到20000HZ。低于20 HZ的声音叫次声波,高于20000HZ的声音叫超声波。
超声波具有许多奇异特性:空化效应——超声波能在水中产生气泡,气泡爆破时释放出高能量,产生强冲击力的微小水柱,它不断冲击物件的表面,使物件表面及缝隙中的污垢迅速剥落,从而达到净化物件表面的目的。传播特性——它的长短,在均匀介质中能够定向直线传播,根据这一特性可以进行超声探伤、测厚、测距、医学诊断等。

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    Thinking about  a future career cm bung a lei of stress. ____This cuts up the question into   workable issues that you and your child can  enjoy dealing with  throughout their  childhood years.Here's how:

    In your child's lift, there are times when they are given the opportunity to see and/or discuss a certain career Schools have Career Day. an aunt or uncle talks about what they  do for a living or your child's youth group goes  on a trip to a hospital und talks to the staff there. ____

    When your Child shows interest in a certain career. you should do some research. Then, you can offer your child some information on that job and related jobs. ____ It is a wonderful the online resource.

    Help your Child weigh the pros and cons for his or her different career interests. Encourage your child to narrow(缩小)the cboice down to five at the most.

    ____ This is a good time to begin ordering in college and  technical school lists. Use the lists and any other information you have found as an ice breaker for more converasations with your child.

    ____ Make this a clear message. Teach your child that part of be ing independent is knowing when and who to lead on,trust and respect.

A.Do you fed you have open communication with your child?

B.The Occupational Oudook Handbook gives you what schooling is needed.

C. The final decision lies with  your child, but you do have the  right to have input.

D. Choosing the right career is one of die mm important decisions  your child will make in life.

E. Figure out the path your child would have to take to obtain the schooling, for his career choices.

F. Each of these nines is an opportunity for you to ask your child what he thought of those jobs or that field of work.

G. Parents  need to learn to help their child conquer this great question by dropping  seeds of  conversation  as time goes by Bud watch them grow into ideas.