Which of the following is an example of a biosignal?

A biosignal is typically defined as any measurable signal that is produced by biological systems and can reflect the physiological state of the body. In this context, an ECG (electrocardiogram) recording measures the electrical activity of the heart, making it a quintessential example of a biosignal because it directly represents the heart's physiological activity.

While a blood pressure reading also originates from a biological system and reflects cardiovascular health, it is more of a measurement or assessment rather than a direct electrical signal. Similarly, monitoring the color of a skin lesion can provide valuable information regarding a patient's health but doesn't involve a measurable biological signal in the same way that an ECG does.

Thus, although blood pressure readings and observations of skin lesions provide important health-related data, the direct physiological representation found in an ECG recording is the primary reason why it stands out as a clear example of a biosignal.