Answer:
C. uppercase Gothic Sans Serif
Explanation:
You want to know the recommended lettering style for drawings conforming to ANSI standards.
Lettering
Lettering on working drawings — those made to describe the manufacture or production of a product — must be legible and free of any ornamentation (sans serif). ANSI standards recommend an uppercase single-stroke Gothic style (Arial font).
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Additional comment
The lettering is called "single-stroke" because each line is the width of one pencil line.
Hand-written lettering is generally formed by top down or left to right strokes, straight or curved as needed. The use of a lettering guide is recommended.