Which of the following is covered by Medicare Part B?

Medicare Part B primarily focuses on outpatient care and services, which include physician visits and outpatient services. This includes visits to healthcare providers for preventive care, diagnostic tests, lab work, and certain treatments not requiring hospital admission. By covering these services, Medicare Part B aims to provide access to necessary medical care for beneficiaries outside of inpatient hospital settings.

Other options, while important aspects of healthcare, fall outside the scope of what Medicare Part B specifically covers. For instance, emergency transportation is typically covered under Medicare Part B, but it is not the primary focus. Hospital stays and surgical procedures are generally covered under Medicare Part A, which deals with inpatient care. Long-term care is not covered by Medicare in general, as it primarily encompasses custodial care, which is not part of Medicare's benefit structure. Therefore, the correct answer emphasizes the role of Medicare Part B in facilitating outpatient healthcare services, which is crucial for patient management and continuity of care.