Correct Answer: A

Rationale: After activating the emergency response system, the immediate priority in CPR is to begin chest compressions to support blood circulation. High-quality chest compressions are crucial in providing oxygen to vital organs, especially the brain, during cardiac arrest. Starting chest compressions promptly can improve the chances of survival for the person in need of CPR. Checking for breathing, performing abdominal thrusts, or assessing pulse should only be done after initiating chest compressions in the CPR sequence.

Correct Answer: C

Rationale: Checking the humidifier's water regularly is the priority precautionary measure that should be done by the nurse during oxygen therapy. Maintaining adequate water in the humidifier ensures proper humidification of the oxygen delivered to the patient, helping prevent mucous membrane dryness and irritation. Dry mucous membranes can lead to discomfort, increased risk of infection, and potential damage to the respiratory system. Therefore, ensuring the humidifier's water level is appropriate is crucial for the safety and well-being of the patient receiving oxygen therapy. Limiting visitors, attaching "No Smoking" signage, and connecting the bait to the oxygen tank are important precautions as well, but checking the humidifier's water is the priority measure in this scenario.

Correct Answer: B

Rationale: The most appropriate action for the nurse to take when noticing that the patient seems anxious and is avoiding eye contact is to ask the patient if they are feeling anxious and if they would like to talk about it. This approach shows empathy, concern, and openness to addressing the patient's emotional state. By directly acknowledging the patient's behavior and giving them the opportunity to express their feelings, the nurse can create a supportive and caring environment that promotes effective communication and trust between the patient and healthcare provider. It is important to consider the patient's emotional well-being alongside their physical health during consultations.

Correct Answer: D

Rationale: The clinical presentation of chest pain, dyspnea, and a friction rub heard on auscultation is suggestive of pericarditis. The diffuse ST-segment elevation seen on the electrocardiogram (ECG) is a classic finding in pericarditis, known as the "universal sign." In contrast, stable angina typically presents with chest pain on exertion that is relieved by rest or nitroglycerin, while unstable angina presents with chest pain at rest or with minimal exertion. Acute myocardial infarction would typically present with ST-segment elevation in specific leads correlating with the area of myocardial ischemia/infarction. However, in the context of diffuse ST-segment elevation and symptoms suggestive of inflammation (friction rub), the most likely diagnosis is pericarditis.

Correct Answer: A

Rationale: Natural killer (NK) cells play a vital role in the innate immune response by identifying and eliminating virus-infected cells, as well as tumor cells, without the need for prior exposure or activation. NK cells are able to detect abnormal cells by recognizing changes in the cell surface molecules, such as downregulation of MHC class I molecules. Once activated, NK cells release cytotoxic granules containing perforin and granzyme, leading to the destruction of the target cell. This direct killing mechanism is crucial for controlling viral infections and preventing the development of tumors. NK cells do not produce antibodies (option B), present antigens to T cells (option C), or release cytokines to recruit other immune cells (option D) as their primary function in the immune response.