A:硫酸钾
B:磷矿粉
C:硝酸铵
D:氯化钾
①向上排空气法 ②向下排空气法 ③排水法.
你看遥远的东西是美丽的,________长距离为人们留下了________的空间,如________的远山,如________的夜空。
I am looking after little Tom today. He's been in my house _ 8:00 this morning.