The study of the heart is called

The study of the heart is called Cardiology. This branch of science focuses on understanding the heart's structure, function, and disorders.

The study of blood and its related disorders is called Hematology, which deals with the blood, its components, and diseases affecting it. Similarly, the study of the circulatory system and the lymphatic system is referred to as Angiology. Meanwhile, the study of cartilage and its anatomy is known as Chondrology.

To summarize, the study of the heart is called Cardiology. Based on the given options, Option D (Cardiology) is the correct answer.