下列电离方程式中正确的是( )
A:NaHCO3=Na++HCO3-
B:Na2SO4=2Na++SO4-2
C:Ca(NO3)2=Ca2++2(NO3)2-
D:KClO3=K++Cl-+3O2-
每年正月初一开斋,这一天称为开斋节。( )
-It’s on the bed.
人体循环系统结构中,不存在瓣膜的是( )
根据问句选答句。
How old are you?____ A. I'm 10.
Happy birthday!____ B. Five.
How are you?____ C. Thank you.
How many boxes?____ D. I'm fine, thank you.
I have a ruler.____ E. Me, too.