A:to his students to arrive
B:to his students for arriving
C:at his students to arrive
D:at his students for arriving
导致“公车上书”的直接原因是( )
如图所示,实验Ⅰ是制备蒸馏水的装置,实验Ⅱ是电解水的装置.
已知样本数据1、2、2、3、7,下列说法不正确的是( )