Final answer:
Lead II provides the clearest recording of the heart rhythm on an electrocardiogram (ECG) because it captures strong signals of the heart's electrical activity.
Step-by-step explanation:
The lead that provides the clearest recording of the heart rhythm on an electrocardiogram (ECG) is lead II. Lead II is obtained by placing the positive electrode on the left leg and the negative electrode on the right arm. This lead is commonly used in ECGs because it provides a strong signal of the heart's electrical activity. Other leads, such as lead I and lead III, can also provide valuable information about the heart's rhythm.