细胞膜的成分中含量较高的物质是( )
A:糖类和水
B:脂质和蛋白质
C:蛋白质和糖类
D:水和脂质
如图甲所示,为测量滑轮组机械效率的实验装置,钩码总重9N.
—Michael was late for Mr. Smith's chemistry class this morning.
—________? As far as I know, he never came late to class.