How can an artist use a pencil to check proportion?

Correct answer: To compare the lengths of different parts

In observational drawing, an artist can hold a pencil at arm's length, align it with a reference part, and use it as a simple measuring guide. The artist can then compare the lengths, widths, or angles of other parts with that reference. Option B is correct. Shading, mixing colour, and cutting paper are not the purpose of this proportional checking method.