ECG depicts the depolarisation and repolarisation process during the cardiac cycle. In the ECG of a normal healthy individual one of the following waves is not represented.

Options

A. Depolarisation of atria
B. Repolarisation of atria
C. Depolarisation of ventricles
D. Repolarisation of ventricles

Answer

To solve the question regarding the ECG (electrocardiogram) and the waves represented during the cardiac cycle, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Components of an ECG**:
- An ECG consists of several waves that represent different electrical activities of the heart.
- The main waves are:
- **P Wave**: Represents atrial depolarization.
- **QRS Complex**: Represents ventricular depolarization.
- **T Wave**: Represents ventricular repolarization.

2. **Identify the Waves Represented**:
- From the above definitions:
- The **P wave** indicates that the atria are depolarizing.
- The **QRS complex** indicates that the ventricles are depolarizing.
- The **T wave** indicates that the ventricles are repolarizing.

3. **Analyze the Options Given**:
- The options provided are:
- A) Depolarization of atria
- B) Repolarization of atria
- C) Depolarization of ventricles
- D) Repolarization of ventricles
- We know that:
- Atrial depolarization (P wave) is represented.
- Ventricular depolarization (QRS complex) is represented.
- Ventricular repolarization (T wave) is represented.
- However, there is no specific wave in the ECG that represents the repolarization of the atria.

4. **Conclusion**:
- The wave that is not represented in the ECG of a normal healthy individual is the **repolarization of the atria** (option B).

### Final Answer:
The correct option is **B) Repolarization of atria**.