The correct choice is (A) reconnaissance.

The Logic Breakdown
- The Clue: The second half of the sentence explains why the artist makes these sketches: "on the basis of these sketches the artist makes a decision on his or her approach."
- The Requirement: We need a word that describes a preliminary survey, an informationgathering mission, or a way to "scout out" a subject before committing to a final plan.
- The Match: Reconnaissance is a term most often used in military contexts to describe a mission to gather information about an enemy or terrain. In an artistic context, it perfectly describes the act of sketching to "scout" the subject's form and lighting before the "main assault" of the final painting.

Why the others fail:
- (B) Caricature: A caricature is a picture that exaggerates certain characteristics to create a comic or grotesque effect. While a sketch could be a caricature, nothing in the sentence suggests the artist is trying to be funny or exaggerated; they are trying to make a "decision on an approach."
- (C) Vignette: A vignette is a brief evocative description, account, or episode. In art, it's a small illustration or portrait that fades into the background without a definite border. It describes a style of finished work, not necessarily an information-gathering sketch.
- (D) Pastiche: An artistic work in a style that imitates that of another work, artist, or period. This doesn't fit the idea of a preliminary study of a specific subject.
- (E) Cameo: A short descriptive literary sketch or a brief appearance by a prominent person in a movie. It doesn't capture the "scouting" nature of the artist's preparation.