Final answer:
Active duty service members may be exempt from completing their PHA in certain situations like combat deployments or medical downgrading.
Step-by-step explanation:
Active duty service members, both officers and enlisted, may not be required to complete a Periodic Health Assessment (PHA) under specific circumstances such as being deployed in combat zones, attending certain military schools, or due to medical downgrading.
Generally, PHAs are mandated assessments to evaluate a service member's medical readiness to perform their duties. However, there are exceptions when the fulfillment of the assessment is either not practical or impossible due to service requirements or locations.