【单选题】实验中的下列操作正确的是
A.
用试管取出试剂瓶中的Na 2 CO 3 溶液,发现取量过多,为了不浪费,把过量的试剂倒入试剂瓶中
B.
用浓硫酸配制一定物质的量浓度的稀硫酸时,浓硫酸溶于水后,应冷却至室温才能转移到容量瓶中
C.
用蒸发方法使NaCl从溶液中析出,应将蒸发皿中NaCl溶液全部蒸干才停止加热
D.
分液操作时,分液漏斗中下层液体从下口放出,上层液体也从下口放出
【简答题】His friends _________ him when he got into trouble.
【单选题】Eric the Red was forced to leave because he had committed a murder, ____ he got into trouble.
【单选题】He was forced to leave Iceland because he had committed a murder, ____ he got into trouble. [ ]
【单选题】在CO与Fe 2 O 3 反应的实验中,下列操作正确的是( )
B.
先给装有Fe 2 O 3 的玻璃管加热,后通入CO,并点燃尾气
D.
实验结束时先停止加热,继续通CO至玻璃管冷却
【单选题】锁相环路电路作用是()
C.
使输出信号幅度保持恒定或仅在很小的范围内变化
【简答题】He got into trouble when he paid his bills with rubber checks.
【单选题】锁相环路电路作用是
C.
使输出信号幅度保持恒定或仅在很小的范围内变化
【简答题】He got into trouble for talking class.