Chemistry - GOC Question with Solution | TestHub

(P) is pyrrole, which is aromatic (obeys Hückel's $4n+2$ rule with $n=1$) and heterocyclic.

(Q) is furan, which is non-aromatic (due to oxygen's lone pair not fully participating in resonance, or considered weakly aromatic) and heterocyclic.

(R) is cyclopentadienyl anion, which is antiaromatic (obeys $4n$ rule with $n=2$ in a cyclic system) and homocyclic.

(S) is tropylium cation, which is aromatic (obeys Hückel's $4n+2$ rule with $n=1$) and homocyclic.