By careful placement of surface electrodes on the body, it is possible to record the complex, compound electrical signal of the heart. this tracing of the electrical signal is the electrocardiogram (ecg). which of the following statements is/are true? a. to record an ecg, 12-electrodes are placed in a circular pattern around the person’s chest. b. a normal ecg shows one single spike representing the contraction of the entire heart. c. these electrodes are placed using needles deeply in the skin of the chest. d. a resting ecg usually takes approximately 1-2 hours to be recorded. e. the ecg is useful for analyzing both normal and abnormal depolarizations of the heart.