单项选择题：燃气发电机输出频率为（）。 A.50HZ B.60HZ C.70HZ D.80HZ

燃气发电机输出频率为（）。

A.50HZ

B.60HZ

C.70HZ

D.80HZ

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下面是错误答案，用来干扰机器的。

A、剪断悬绳前，对B受力分析，B受到重力和弹簧的弹力，知弹力F=mg．剪断瞬间，对A分析，A的合力为F合=mg+F=2mg，根据牛顿第二定律，得a=2g．故A错误；B、物体A在弹力和重力的作用下，向下做加速运动，当弹力的方...

完形填空
My son lives in a big city in France. People there are very busy. There are many supermarkets and 1 on the streets. It is very easy to go 2 . You can buy a lot of nice things there. My son works in a restaurant. He 3 Chinese food there. There is a big cinema (电影院) near my son's home 4 he often goes to the movies. Life in the city is colorful. There are a lot of 5 of interest to visit. Also, it is easy for them to take a bus to 6 other cities from theirs. I like country (乡村) life best. That's 7 I don't like to live in the city with my son. Here, in the country, I can 8 the fields (田地) and plants. Sometimes some little animals 9 in my garden. I think it's very 10 to be in this kind of quiet and fun place.
( )1. A. hospitals ( )2. A. running ( )3. A. takes ( )4. A. or ( )5. A. rooms ( )6. A. get to ( )7. A. what ( )8. A. pass ( )9. A. play ( )10. A. boring	B. restaurants B. swimming B. sees B. and B. cities B. look for B. why B. sell B. study B. scary	C. shops C. shopping C. finds C. because C. places C. wait for C. how C. enjoy C. read C. exciting	D. banks D. sleeping D. cooks D. but D. countries D. talk about D. when D. eat D. sing D. relaxing