—No. You______. There will be plenty of time.
A:mustn't
B:can't
C:couldn't
D:needn't
Can I help you?
选项
待提纯的物质
除杂的试剂
操作方法
A
NO2(NO)
O2
收集气体
B
CO2(HCl)
饱和Na2CO3溶液
洗气
C
FeCl2溶液(FeCl3)
足量铁粉
过滤
D
KCl溶液(MgCl2)
NaOH溶液