Which of these terms best describes a technique in which lines are places in parallel series to darken the value of an area?

Answer is hatching.

Explanation:

Hatching is one of the techniques used art, especially the aspects that deal with drawing. It is considered or described to be a method of using parallel lines to shade areas of a diagram or drawing.

Hatching is known to be the best easiest way for those that make drawings or diagram with pencil, and pen-and-ink. This is because it makes their work neat and clean.