Correct choice is (c) Quasi – Periodic
Explanation: ECG wave comprises PQRSTU segments. In this, P, R, T, U are all waves that go above the baseline and Q, S are waves that go below. However, P wave and R wave are not periodic. Periodicity is checked between the successive R waves. Quasi periodic waves are those which are periodic in a certain interval. Since the ECG signal is periodic in R to R interval or P to P interval, its a Quasi periodic wave.