A:what do you want?
B:may I have your order?
C:this table is reserved.
D:I would like to serve you.
下列关于呼吸作用的叙述正确的是( )
下列各组微粒具有相同的质子数和电子数的是( )
物体从离地45m的高处作自由落体运动(g取10m/s2).求