The correct answer is: C. Level
A level is a tool used to measure the vertical or horizontal position of a surface. It is used in construction to ensure that surfaces are level, and in surveying to measure the elevation of points on the Earth’s surface.
A magnetic compass is a device used to find direction. It consists of a magnetized needle that aligns itself with the Earth’s magnetic field. The needle points north, which can be used to find direction.
A theodolite is an instrument used to measure angles in the horizontal and vertical planes. It is used in surveying and engineering to measure the angles between objects.
A clinometer is an instrument used to measure angles of slope. It is used in surveying and engineering to measure the slope of surfaces.
In the context of laying sewers, a level is used to ensure that the sewer is laid at a consistent depth. This is important to ensure that the sewer is properly drained and does not leak.