问题
选择题
电磁波与机械波具有的共同性质是（ ）
A．都能传输能量
B．都能在真空中传播
C．都是横波
D．都具有恒定的波速
答案
答案：A
题目分析：电磁波和机械波在传播过程中都能即传播信息又传播能量，电磁波可以在真空中传播，机械波不能再真空中传播，B错误；电磁波是横波，机械波既有横波又有纵波，C错误；机械波在不同的介质中的传播速度不同，D错误；
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电磁波与机械波具有的共同性质是（ ）
A．都能传输能量
B．都能在真空中传播
C．都是横波
D．都具有恒定的波速
答案：A
题目分析：电磁波和机械波在传播过程中都能即传播信息又传播能量，电磁波可以在真空中传播，机械波不能再真空中传播，B错误；电磁波是横波，机械波既有横波又有纵波，C错误；机械波在不同的介质中的传播速度不同，D错误；
It was one of the happiest Saturday mornings I had spent with my daughter, Gigi. That was, until two strangers threw her into their car and sped away. It seemed like a bad dream.I could ____ speak when the police questioned me. After that, the policeman asked me to go home to wait. My friend Gloria came to ____me. She took my hand and gave me ____. It was a picture of a little girl ____asleep in her bed, standing by the bed was a tall, blond(金发的)__ __. We prayed and waited by the phone until sunset. The ____ never rang. Suddenly，the front door swung open. I looked up and ____. There stood Gigi. I cried, throwing my ____ around her. Gigi said：“I was scared. We were going really fast on an old ____ road I'd never seen before. But then a tall man walked out ____ the car，and they ran off the road and hit a tree. Then the tall man ____ the car door and pulled me out. He was really nice，and said I would be okay. I must have gone to ____， because when I woke up it is in front of our house. He must have brought me home.” “But who...how did he know..., where to bring you？”My voice broke. Gigi ____ her head. Just then Gigi noticed Gloria's picture. “That's him！” she ____ at the picture. “Mommy，that's the man who pulled me out of the car！” Gloria and I turned ____. “Are you sure that's the man？” Gloria asked. “Yeah, that's him ____ that he didn't have wings，and he was wearing blue jeans.” Later that night, the police found the____kidnappers. When questioned, the driver remembered turning away to ____ hitting a tall blond man. Twenty years have gone by. We have never heard from any one claiming to have ____Gigi. There have been no logical explanations for her ____. But from that day on, I believe that all experiences, positive and negative, are given to us for our strengthening and learning.
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