Final answer:
The most suitable treatment for a 29-year-old male with a severe headache and nausea, who has a history of migraine headaches, is to assist with migraine medication and transport to a healthcare facility without the use of lights and siren to avoid exacerbating symptoms.
Step-by-step explanation:
Given the symptoms and the history of migraine headaches as diagnosed by a physician, the best course of action for treating a 29-year-old male complaining of severe headache and nausea would be option (a) assisting him with his migraine medication and transporting without lights and siren. This approach offers a quiet environment, which can be beneficial for patients suffering from migraines, as loud noises and bright lights can often exacerbate their symptoms. It's important to ensure the comfort of the patient and monitor his condition en route to the healthcare facility.
However, if the patient presents signs that are unusual for his migraine or if he shows any new or alarming symptoms, such as confusion, severe sudden headache, vision changes, trouble speaking, or one-sided numbness or weakness, more emergent transport might be warranted due to the possibility of a more serious condition like a stroke. Such symptoms necessitate immediate medical attention in a hospital setting.