The correct option is (c) ECG
To elaborate: A Cardiac monitor is specifically useful for monitoring patients with cardiac problems and the special areas in the hospitals where they are generally used are known as cardiac care units or coronary care units (CCU). These instruments are also called ‘Cardioscopes’ and comprise of disposable type pregelled electrodes to pick up ECG signal. Amplifier and a cathode ray tube (CRT) for the amplification and display the ECG which enable direct observation of the ECG waveform.
