Enlargement of auricles refers to an increase in the size of the atria of the heart. This condition can be observed on an electrocardiogram (ECG) as an enlargement of the P-wave. The P-wave represents the depolarization (contraction) of the atria, so an enlargement of the P-wave indicates increased electrical activity in the atria.

Here is a detailed explanation:

1. Enlargement of the auricles:
When the atria of the heart become enlarged, it can be a sign of certain cardiac conditions such as atrial fibrillation, atrial flutter, or atrial hypertrophy. Enlarged atria are often associated with volume overload or pressure overload on the heart.

2. Electrocardiogram (ECG):
An ECG is a graphical representation of the electrical activity of the heart. It is a diagnostic tool that helps in identifying various cardiac abnormalities. The ECG consists of several waves and segments that represent different phases of the cardiac cycle.

3. P-wave:
The P-wave on an ECG represents the depolarization (contraction) of the atria. It shows the electrical activity originating in the sinoatrial (SA) node and spreading through the atria, causing them to contract. The P-wave is the first positive deflection on the ECG.

4. Enlargement of P-wave:
When the atria become enlarged, there is increased electrical activity in the atria. This increased activity is reflected in the P-wave on the ECG. Enlargement of the P-wave is characterized by an increase in its amplitude and duration.

5. Other options:
a) Enlargement of QR segment: The QR segment is not directly related to the atrial activity. It represents the time between the depolarization of the ventricles and the repolarization of the atria. Therefore, it is not affected by the enlargement of the auricles.
b) Depression of ST segment: The ST segment represents the time between ventricular depolarization and repolarization. It is not directly related to atrial activity or the enlargement of the auricles.
c) Elevation of ST segment: Similar to the depression of the ST segment, the elevation of the ST segment is not associated with atrial activity or the enlargement of the auricles.

In conclusion, the correct answer is option 'A' - Enlargement of the P-wave. Enlargement of the auricles is reflected in the P-wave on an ECG as an increase in its amplitude and duration. This finding can help diagnose various cardiac conditions related to atrial enlargement.