Final answer:
Setting a broken arm is identified as the best example of medical treatment as it directly involves treating an injury.
Step-by-step explanation:
The action that could best be described as medical treatment is setting a broken arm. This is because medical treatment involves active intervention to treat an illness or injury. Setting a broken arm is a direct form of care that helps ensure proper alignment of the bone for healing. In contrast, simply observing a heat stroke victim is not an active treatment; it is an assessment or monitoring action. Medical treatments can also involve the use of technology such as magnetic resonance imaging (MRI) or computed tomography (CT) scanning in order to diagnose conditions, which is a precursor to treatment but not treatment itself.