A:ZXY3
B:ZX2Y6
C:ZX4Y8
D:ZX8Y12
探究影响滑动摩擦力大小因素的实验装置如图所示.在小桶内装入适量的沙子,滑块恰好在水平木板上做匀速直线运动.
—I want to see Mr. White. We have an appointment.
—I'm sorry, but he is not ________ at the moment, for the meeting hasn't ended.
如图中,能正确表示某食物链中生物数量关系的是( )