Solution

(a) Number of $$\pi$$ electrons $$=4$$
$$\because$$ It is not equal to $$4n + 2$$
$$\therefore$$ It is not an aromatic compound

(b) Number of $$\pi$$ electrons $$= 6 (= 4n + 2)$$
(Here lone pair of electrons of N does not involve in delocalisation)

(c) Number of $$\pi$$ electrons
$$= 4 + 2 = 6 ( = 4n + 2)$$

(d) Number of $$\pi$$ electrons $$= 6 ( = 4n + 2)$$
Thus, except $$1, 3-cyclobutene$$, all species are aromatic in nature.

Hence option A is correct.