具有α-羟基酮结构的药物是（）
A．左炔诺孕酮
B．米非司酮
C．黄体酮
D．炔诺酮
E．醋酸地塞米松
参考答案：E
如图所示，将两条完全相同的磁铁（磁性极强）分别固定在质量相等的小车上，水平面光滑，开始时甲车速度大小为3m/s，方向水平向右，乙车速度大小为2m/s，方向水平向左，两车在同一直线上，当乙车的速度为零时，甲车速度为________m/s，方向________。
She ________ her story at the point where she stopped just now. [ ]
A. took up
B. took down
C. took on
D. took off
