El vecino del lado construye edificios, pero no es carpintero. a. él es ingeniero. c. él es cocinero. b. él es mecánico.

The sentence El vecino de al lado construye edificios, pero no es carpintero translates into The next-door neighbor builds buildings, but he isn't a carpenter. So the logical answer is that this man is an engineer. It is likely that this neighbor is a civil engineer because this is an engineer who designs and maintains roads, bridges, dams, buildings and similar structures.