题干
-- Is Lily thirsty?
--
A：No, she doesn't.
B：Yes, she is.
C：No, she can't.
答案(点此获取答案解析）
B
-- Is Lily thirsty?
--
A：No, she doesn't.
B：Yes, she is.
C：No, she can't.
，y为该点到地面的距离，c为常数，B0为一定值．铝框平面与磁场垂直，直径ab水平，(空气阻力不计)铝框由静止释放下落的过程中( )