A:氨气极易溶于水,可以用来做喷泉实验
B:氨气的还原性可以解释氨气与氯化氢的反应实验
C:实验室可用NH4Cl和石灰水制取氨气
D:NH3液化时放出大量的热,因而,不能用氨作制冷剂
① {2x=yx+y=2 ;② {2x+y=42x2−y=1 ;③ {2x+y=4z−3=5 ;④ {x=1y=1 .
①一段烟囱(无烟囱帽);②一段圆钢;③铅锤;④烟囱帽.①②都呈 ____的形状;③④都呈____ 的形状.
从方框中选择恰当的语句,补全对话。
A.Yes, she is.
B.He's my brother.
C.No, he isn't.
D.He's my brother.
Cheng Jie: Who's that boy?
Amy:____
Cheng Jie: Is she your mother?
Cheng Jie: Is he your father?