Final answer:
Dexamethasone is the drug most likely to be prescribed to a patient with a brain tumor to reduce edema. It is a corticosteroid that decreases immune response and inflammation, differing from diuretics which act on blood pressure and kidney function.
Step-by-step explanation:
The patient with a brain tumor experiencing edema is most likely to be prescribed C. Dexamethasone. Dexamethasone is a corticosteroid, which is used to reduce inflammation and edema by decreasing the body's immune response. Unlike the diuretics b. and d., which act on the kidneys and the loop of Henle to manage blood pressure by altering the reabsorption of Na+ and Cl-, dexamethasone works by its anti-inflammatory effects, which make it effective for reducing the swelling around brain tumors.