The correct answer is B. Anatomy.
Anatomy is the study of the structure of organisms and their parts. It is a branch of biology that deals with the physical form of organisms and their organs and tissues. Anatomy is important for understanding how organisms function and how they interact with their environment.
Morphology is the study of the form and structure of organisms. It is a branch of biology that deals with the external features of organisms, such as their shape, size, and color. Morphology is important for understanding how organisms have adapted to their environment.
Histology is the study of the microscopic structure of tissues. It is a branch of biology that deals with the cells and tissues that make up organisms. Histology is important for understanding how organisms function and how they develop.
Cytology is the study of cells. It is a branch of biology that deals with the structure, function, and behavior of cells. Cytology is important for understanding how organisms function and how they develop.
In conclusion, the study of internal structure of organism is called anatomy.