________in the queue for half an hour,the old man suddenly realized he had left the cheque in the car. ( )
A:Waiting
B:To wait
C:Having waited
D:To have waited
如表欲除去下列物质中混有的少量杂质(括号内为杂质),所选试剂和方法均正确的是( )
选项
混合物
试剂
方法
A
H2(HCl)
饱和NaHCO3
洗气、干燥
B
CaCl2溶液(盐酸)
足量CaCO3
过滤
C
CuO(Cu)
适量CaCO3
D
CaO(CaCO3)
水
过滤、洗涤、干燥
下列各项划线字读音完全正确的一项是( )