​The study of cells is called _____________.

Correct option is A

The correct answer is (a) Cytology.

Cytology is the branch of biology that deals with the structure, function, and behavior of cells.

It involves the study of:

• Cell anatomy (structure)
• Cell physiology (function)
• Cell interactions and life cycle

Information about the other options:

• Serology: The study of blood serum, especially concerning immune responses and the detection of antibodies.
• Cytoplasm: Refers to the gel-like substance inside the cell membrane, not a study field.
• Etiology: The study of causes or origins of diseases, not specifically related to cells.

Additional Information:

Cytology is foundational to modern biology and medicine, enabling the understanding of diseases at the cellular level, such as cancer and genetic disorders.