Zoology - Body Fluids and Circulation Question with Solution | TestHub

Option (2) is the answer because, the P-wave represents the electrical excitation (depolarisation) of the atria which leads to the contraction of both the atria. The QRS complex represents the depolarisation of the ventricles. The T-wave represents the return of the ventricles from excited to normal state (Repolarisation). The end of the T-wave marks the end of systole.