(a) (Acenaphthene)


$$\to$$ 10 $$\pi$$e^$$-$$ in cyclic conjugation

$$\Rightarrow$$ Aromatic

"Note: For a compound with multiple cyclic rings to exhibit aromaticity, it must conform to Hückel's rule, which stipulates that the molecule should have (4n+2) π-electrons in the largest periphery of continuous conjugation. Rings with sp³ hybridized carbon atoms are not considered in this context. Despite their potential π-bonds, these rings cannot participate in resonance with π-bonds of the other rings due to the sp³ hybridization, and thus do not contribute to the overall aromaticity of the compound."

(b)
$$\to$$ 4 $$\pi$$e^$$-$$ in ring conjugation $$\Rightarrow$$ Anti Aromatic

(c)
$$\Rightarrow$$ 4 $$\pi$$e^$$-$$ in ring conjugation $$\Rightarrow$$ Antiaromatic

(d)
6$$\pi$$e^$$-$$ in ring conjugation $$\Rightarrow$$ Aromatic