During yоur Internаl Medicine rоtаtiоn, you аre asked to evaluate an HIV-positive patient who has returned to the office infrequently for scheduled medical follow-up appointments during the past year. At the time of his last visit ten months ago, the patient had a CD4 count > 500. Current laboratory studies reveal that the patient now has a CD4 count < 100. Your preceptor informs you that the patient will need to be started on Pneumocystis jirovecii pneumonia prophylaxis. You may assume that the patient has no known drug allergies. Which of the following medications is generally recommended as the treatment of choice for Pneumocystis pneumonia (PCP) prophylaxis?