A:Na2O
B:Na2O2
C:Na2O和Na2O2
D:Na2O2和NaO2
在一根长为884m的铁管一端重重敲击一下,在铁管另一端的人能听到两次声音,声音的间隔2.43秒。声音在铁管里的传播速度是多少?
Sue was so _______ her holiday that she couldn't stop talking about it.