Final answer:
Yes, it is acceptable to draw a standing subject as long as the arm is well-supported, which is demonstrated by the mechanics of the human body and the efficient use of forces and balance to maintain stability.
Step-by-step explanation:
It is acceptable to draw a standing subject as long as the arm is well-supported is a statement that reflects the principles of physics, specifically when discussing the mechanics of the human body in different postures and the forces involved. For example, the forearm of a person holding a book with the biceps exerting force to support the weight, is an illustration of the arm being well-supported. Similarly, when a person is standing with limbs extended and the feet positioned to maintain balance, as described in various figures within the context, it showcases how muscles and posture can distribute the load optimally to support the arms and maintain balance. Variations instance, such as sitting or kneeling, where the photographer braces her arm and elbow on her knee, is an example of how the body adapts support mechanisms for stability. This can also be related to how individuals adjust their stance to maintain balance by positioning their center of gravity over the base of support, as seen with various examples of people carrying different loads.