问题
选择题
—What are you doing, my dear?
—I am ________ for my glasses. I remember I have put it on the bookshelf.[ ]
A. searching
B. feeling
C. finding
D. looking
答案
答案：D
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—What are you doing, my dear?
—I am ________ for my glasses. I remember I have put it on the bookshelf.[ ]
A. searching
B. feeling
C. finding
D. looking
答案：D
，圆形匀强磁场的半径R=
，重力忽略不计。求：