This is a test of commonsense with single/multi-choices. Complete the next sentence:

How to measure parallelism
Define the surface for testing.
Parallelism is a quality that can be tested on several different types of surfaces. These are labeled based on their positions relative to each other.

A. If the lines in an object vary greatly, then they may indicate a parallelism. For glass object measurements, buy a large glass. B. The surface of a given sheet of paper can be drawn using an electrical pen drawn from the object (object title for the testing sheet). The surface of an object is measured by moving the pen along the surface until you see the positive difference in the surface. C. You may wish to test parallelism of the following : Planar surface: opposite flat surfaces of a rectangular solid need to be parallel to each other. Cylindrical surface: a cylinder appears round when looking at its end, but when held upright, its sides must be parallel for the cylinder to function properly. D. Light dust characterized by light dust circling animals is considered solid light and light dust floating. Ammonia children also have cloud-white particles spinning on concrete in crevices.
The answer is:
C.