Final answer:
Accessory muscles involved in forced inhalation during exercise or heavy breathing include neck muscles like the scalenes and abdominal muscles such as the obliques, not the options provided (A to D).
Step-by-step explanation:
The accessory muscles that aid inhalation during exercise or forced ventilation are not found among the options provided in the question (options A to D). During normal breathing, the primary muscles involved are the diaphragm and external intercostal muscles. However, during forced breathing or hyperpnea, such as when exercising or during voluntary maneuvers like singing, additional accessory muscles are recruited. The accessory muscles include the scalenes and sternocleidomastoid muscles in the neck, which help lift the thoracic wall, thus increasing lung volume for forced inspiration. The abdominal muscles, including obliques, and the internal intercostal muscles play a role in forced expiration by compressing the ribcage and forcing abdominal organs upward against the diaphragm, helping to push air out more forcefully.