Which trade in the Entrance Exam 2 is primarily engaged in maintaining and constructing walls and roofs?

The trade primarily engaged in maintaining and constructing walls and roofs is the carpenter. Carpenters are skilled tradespeople who work with wood and other materials to build and install frameworks, structures, and other components of buildings. This includes tasks such as framing walls, constructing roof structures, installing doors and windows, and finishing surfaces. Their expertise in working with materials to create durable and functional structures makes them the key professionals for these specific construction elements.

The other trades listed focus on different areas of construction. Insulators specialize in applying insulation materials to improve energy efficiency in buildings. Concrete finishers work with concrete to shape and finish surfaces, which does not typically involve walls and roofs in the same context as carpentry. Electricians focus on electrical systems, installations, and maintenance, which are not directly related to the construction of walls and roofs. Thus, carpenters are the appropriate choice for this question.