Which element is oxidized and which is reduced in the following reactions

Which element is oxidized and which is reduced in the following reactions? ( Express your answers as chemical symbols separated by a comma. Enter the oxidized element first.)

a) N2(g) +3H2(g) -----> 2NH3(g)

b) 3Fe(NO3)2 (aq) +2Al (s) --------> 3 Fe(s) +2 Al(NO3) 3 (aq)

c) Cl2(aq) + 2 NaI (aq) ------> I2 (aq) + 2NaCl(aq)

d) PbS (s) + 4H2O2 (aq) ------> PbSO4(s) + 4 H2O (l)

a/ N2 is a reductor and it's oxydized in the reaction
N2(0) - 2x3e- ---------> 2N(3+)

b/Al is a reductor and it's oxydized in the reaction
Al(0) - 3e- -------->Al(+3)

c/ I is a reductor and it's oxydized in the reaction

2xI(-1) - 2x1e- ---------> I2(0)

d/ S is a reductor and it's oxydized in the reaction.

S(-2) - 8e- ----------> S(+6)

So:

a/N, H
b/ Al, Fe
c/ I, Cl
d/ S, O

I wrote the oxydative reactions so you'll understand why it is like that. Try doing the reductive :)