Option (a) is correct.
A reducing agent is the one which loses electrons to other substance.
Here, Zn has oxidation number 0 in the L.H.S of the equation, but on R.H.S its oxidation number is +2 i.e. it Zn has donated two of its electrons to

.
Hence, Zn is the reducing agent here.
B - brown eyes
b - blue eyes
If we were to fill out a punette square each of his sex cells would contain at least one brown eyed gene.
D I think.. hopefully it helps a little
Mitochondrion (mitochondria)