Which of the following are characteristics of aromatic compounds?

I. They should be planar.

II. They should follow (4n + 2) π-electrons rule.

III. They should be cyclic.

Select the correct answer using the code given below.

For a compound to be classified as aromatic, it must fulfill four specific criteria:

1. Cyclic: The molecule must contain one or more rings of atoms.
2. Planar: The molecule must be flat (planar) so that p-orbitals can align and overlap to form a continuous π-system.
3. Complete Conjugation: Every atom in the ring must possess an unhybridized p-orbital.
4. Hückel's Rule: The system must contain (4n + 2) π-electrons, where n is a non-negative integer (0, 1, 2, ...).

Benzene (C6H6) is the most common example, having 6 π-electrons (n = 1). If a cyclic, planar, and conjugated system has 4n π-electrons, it is considered anti-aromatic. Since all three statements (I, II, and III) are essential requirements for aromaticity, the correct answer is D.