A = Planar ring, all atoms of the ring sp2 hybridised, has six delocalised π electrons, follows Huckel rule. It is aromatic.
B = Has six π electrons, but the delocalisation stops at sp3 hybridised CH2- carbon. Hence, not aromatic.
C = Six delocalised π-electrons (4 π electrons + 2 unshared electrons on negatively charged carbon) in a planar ring, follows Huckel’s rule. It is aromatic.
D = Has only four delocalised π-electrons. It is non aromatic.
E = Six delocalised π-electrons follows Huckel’s rule. π electrons are in sp2 hybridised orbitals, conjugation all over the ring because of positively charged carbon. The ring is planar hence is aromatic.
F = Follows Huckel’s rule, has 2 π electrons i.e. (4n+2) π-electrons where (n=0), delocalised π-electrons. It is aromatic.
G = 8π electrons, does not follow Huckel’s rule i.e., (4n+2) π-electrons rule. It is not aromatic.