下列物质的制备,能由一步反应实现的是( )
A.KNO3→KOH
B.Fe2O3→Fe(OH)3
C.Cu→Cu(NO3)2
D.CaCO3→Ca(OH)2
答案:C
There were signs here and there, _____ people to look out for ___rocks.
A.warned; fallen
B.warning; fallen
C.warning; falling
D.warned; falling
— Good morning. Can I help you?
— I’d like to have this package .
A.to weigh
B.to be weighed
C.weigh
D.weighed