韶山4型电力机车轴箱为保证其内中外弹簧组合受力均匀,应对其选配,要求3组弹簧在各自工作负荷下高度差()。
A.≤3mm
B.≤4mm
C.≤5mm
D.≤6mm
参考答案:A
盐酸溶液应该盛装在哪种试剂瓶中:()?
A.大口试剂瓶
B.小口试剂瓶
C.两种试剂瓶都可以
In time of serious accidents, we know some basic things about first aid, we can save lives. [ ]
A.whether
B.until
C.if
D.unless