Final answer:
A nurse should consult an EKG lead placement chart to properly place electrodes for a 12-lead ECG, which involves six chest electrodes and four limb electrodes.
Step-by-step explanation:
A nurse who is unfamiliar with the placement of EKG leads should consult a C) EKG lead placement chart to learn the correct placement of electrodes for an electrocardiogram. In a standard 12-lead ECG, six electrodes are placed on the chest, and four electrodes are placed on the limbs. This type of chart will provide the necessary visual aid and instructions to ensure the accurate recording of the heart's electrical activity, which is critical for diagnosing and monitoring patients' cardiac conditions.