It is the study of internal organs of organisms.

Anatomy
Physiology
Morphology
Cell Biology

The correct answer is A. Anatomy.

Anatomy is the study of the structure of an organism, especially the human body. It is a branch of biology that deals with the physical form of organisms and their parts. Anatomy is concerned with the identification, description, and study of the structures of organisms and their relationship to each other and to their function.

Physiology is the study of the function of an organism, especially the human body. It is a branch of biology that deals with the processes of life and the physical and chemical changes that occur in living organisms. Physiology is concerned with the study of how the body works and how its parts interact with each other.

Morphology is the study of the form and structure of organisms. It is a branch of biology that deals with the shape and structure of organisms and their parts. Morphology is concerned with the study of how the body is shaped and how its parts are arranged.

Cell biology is the study of cells. It is a branch of biology that deals with the structure, function, and behavior of cells. Cell biology is concerned with the study of the basic unit of life and how it works.

In conclusion, the correct answer is A. Anatomy. Anatomy is the study of the structure of an organism, especially the human body. It is a branch of biology that deals with the physical form of organisms and their parts.