题干

如图所示,一闭合的小金属环用一根绝缘细杆挂在固定点O处,使金属圆环在竖直线OO′的两侧来回摆动的过程中穿过水平方向的有界匀强磁场区域,若悬点摩擦和空气阻力均不计.则(   )

A:金属环每次进入磁场区都有感应电流,而离开磁场区没有感应电流

B:金属环进入磁场区域后越靠近OO′线时速度越大,而且产生的感应电流越大

C:金属环开始摆动后,摆角会越来越小,摆角小到某一值后不再减小

D:金属环在摆动一段时间后将停在最低点

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C

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    When high school started, Sally and I became best friends. We shared many interests and quickly became very close.When high school ended, we both cried because we would enter different 1 in autumn.

    Our first term of college life was 2, so we often sent long e-mails and encouraged each other. We missed each other so much! In the second term, I found some new friends and I felt very 3 with them. These were friends with whom I could be myself and pour out my feelings. I wanted to share my new friends with Sally.

    When Sally 4 visited me at my school, we were excited.

    She brought a toy bear to me 5a present and told me about her college life. 6, something unexpected happened when I introduced her to my new friends.Her eyes grew dark and I could see the sadness in them.My new friends tried to share their friendship, but Sally seemed unwilling to accept it.I didn't understand 7the people I loved most couldn't love each other.

    Sally left. I knew she was not happy. I thought long about what had happened. I asked her many questions but she didn't answer me. I 8 that she was jealous(嫉妒). She saw me with my new friends and was afraid that we no longer shared the same experiences. She saw that I could still enjoy myself  9 her and wished she could be a part of it.

    I wrote Sally a letter to 10 she's always my best friend. I told her everyone had friends from home and friends from school, and all the friends were indeed life's greatest 11.Sally wrote me back soon. She was in agreement and felt sorry about 12 she had done.

    I think Sally and I both 13 an important lesson from it. Nothing can influence our 14  and change the experiences we've shared.We are now walking on two different paths of life. While new friends are special and exciting, old friends are 15 there, waiting to share their heart, no matter how far away they are from each other.