起重机按取物装置可分为（）种。
A、2
B、3
C、4
D、5
参考答案：D
I can guess you were in a hurry. You _____________ your sweater inside out .
A．had worn
B．are wearing
C．were having on
D．were dressing
A．CD为一窄缝
B．CD为一圆孔
C．比较得到乙、丙两图时的d，乙图的d较小
D．比较得到乙、丙两图时的d，丙图的d较小
