A:Fe2O3+N2O5
B:Fe2O3+NO2 +O2
C:FeO+NO2
D:Fe2O3+N2O 5 +O2
A:What's that?
B:It's a parrot.
DNA上有指导生物发育的全部信息,它主要存在于( )
She thinks that the opera____ understand.