Question

______________ is the art of building.

Answer 1

Your choices are out of order, but I believe the answer is c. Architecture. It is not architect because that is a person who designs the buildings. 
Hope that helped you.

Answer 2

Architecture is the art of building. But it is also the technique of designing and building.  Architecture serves both utilitarian and aesthetic ends. Utilitarian because it fulfills practical requirements and aesthetic because it fulfills expressive requirements. An architect is a licensed person who leads a team in the planning and design of a building or house.