Question

the definition of electrocardiogram is
a record of the electrical activity of the brain
a record of the electrical activity of the lungs
a record of the electrical activity of the heart

Explanation:

An electrocardiogram (ECG or EKG) is a test that records the electrical activity of the heart. It is not related to the electrical activity of the brain or lungs.

Answer:

a record of the electrical activity of the heart