Which of the following services is usually covered by Medicare Part A?

Medicare Part A primarily covers services related to hospital stays and inpatient care. This includes emergency room visits that result in inpatient admission, which is why the choice indicating emergency room visits is correct. When a patient requires immediate medical attention and is subsequently admitted to a hospital, the costs associated with that emergency visit fall under Medicare Part A coverage.

In contrast, routine vision check-ups are typically not included in Medicare Part A, as they are considered preventive services usually covered under other programs. Acupuncture treatments also fall outside of Part A coverage since they are generally not regarded as a standard medical treatment necessary for inpatient care. Long-term care in a nursing home may be covered partially by Medicare, but only in specific circumstances, such as following a hospital stay and for a limited duration; otherwise, it may not fall under Part A. Thus, emergency room visits are the only choice that aligns directly with the coverage provided by Medicare Part A for immediate, necessary medical care.