Calcium imide on hydrolysis will give gas (B) which on oxidation by bleaching powder gives gas (C). Gas (C) on reaction with magnesium gives compound (D). (D) on hydrolysis gives again gas (B). (B), (C) and (D) are:
a. NH3,N2,Mg3N2
b. N2,NH3,MgNH
c. N2,N2O5,Mg(NO3)2
d. NH3,NO2,Mg(NO2)2