A client with coronary artery disease (CAD) is admitted to the medical unit for testing. The client describes having had frequent episodes of angina over the last few days prior to admission. The client is now experiencing shortness of breath, nausea, and chest pressure. After obtaining the client's vital signs, which action should the nurse take next?

A. Applying oxygen via nasal cannula and ensuring oxygen saturation is above 93% is the priority action to alleviate hypoxia and reduce the workload on the heart, especially with the client’s symptoms of angina and shortness of breath. B. While creating a calm environment is beneficial, it does not address the immediate concerns of oxygenation and potential cardiac issues. C. Counting and recording premature ventricular contractions is important, but it is not the immediate priority compared to oxygenation. D. Verifying troponin level assessments is necessary for cardiac monitoring, but immediate oxygen support takes precedence over lab tests.