我国使用“长征3号甲”运载火箭的动力是由高氯酸铵(NH4ClO4)分解所提供的,反应方程式为2NH4ClO4N2↑+Cl2↑+4X↑+2O2↑,则X的化学式为 ( )
A:NH3
B:H2
C:H2O
D:HCl
Tommy, don't play a joke _____ the little boy, he is very shy