Final answer:
For a patient feeling faint, laying them down with legs elevated is the recommended immediate action to increase blood flow to the brain and alleviate faintness, which is related to orthostatic hypotension.
Step-by-step explanation:
When a patient is feeling faint, the most effective immediate action to assist them is C. laid down legs elevated. This procedure involves having the patient lie down flat on their back and then elevate their legs slightly. Elevating the legs helps in increasing blood flow to the brain, which can alleviate feelings of faintness. This is important to counteract the effects of orthostatic hypotension, a condition where blood pressure drops when a person stands up from sitting or lying down, resulting in dizziness or lightheadedness. On the contrary, sitting up might not aid in blood flow to the brain as effectively and could prolong or aggravate the feeling of faintness.