Final answer:
The principle of design in art that is not included is color.
Step-by-step explanation:
The correct answer is d. color.
All of the other options: proportion, emphasis, rhythm, and color are principles of design in art. Proportion refers to the size relationship between different elements in a composition. Emphasis is used to create a focal point or draw attention to a specific area. Rhythm is a visual flow created by repeating elements. And color is an essential component of design that conveys emotion and adds visual interest.
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