Aclient is admitted to the emergency department with chest pain and doesn't respond to nitroglycerin. the health care team obtains an electrocardiogram and administers i. v. morphine. the health care provider also considers administering alteplase. this thrombolytic agent must be administered how soon after onset of myocardial infarction (mi) symptoms? a) within 6 hours b) within 12 hours c) within 24 to 48 hours d) within 5 to 7 days