已知两瓶气体,分别是HCl和Cl2。可以区别它们的方法或试剂是① 观察颜色 ②打开瓶盖看有无白雾 ③湿润的淀粉试纸 ④湿润的红色石蕊试纸 ⑤湿润的蓝色石蕊试纸 ⑥硝酸银溶液
It is often ______ that human beings are naturally equipped to speak.
I can’t leave. She told me that I ______ stay here until she comes back.
—— Do you mind my opening the window? It’s a bit hot in here. —— ______ , as a matter of fact
It’s high time you had your hair cut ; it’s getting _______ .
My friend showed me round the town, ______ was very kind of him.