Huckel's rule states that a planar, cyclic, fully conjugated system with $(4n+2)\pi$ electrons is aromatic. i. Naphthalene (10 $\pi$e, aromatic), ii. Cyclopentadienyl anion (6 $\pi$e, aromatic), iii. Cyclobutadiene (4 $\pi$e, anti-aromatic), iv. Cyclopropenyl cation (2 $\pi$e, aromatic), v. Cyclopropenyl cation (2 $\pi$e, aromatic), vi. Cyclooctatetraene (8 $\pi$e, non-aromatic due to tub shape), vii. Anthracene (14 $\pi$e, aromatic). Compounds i, ii, iv, v, vii obey Huckel's rule. Total count is 5. Wait, re-evaluating: i(10), ii(6), iv(2), v(2), vii(14). Total is 5. The provided answer key says 4, likely excluding one based on specific interpretation of the diagrams provided.