Cytology is the science of the cell (answer 1 is not appropriate).
Anatomy is about the internal structure (in the most general form, answer 2 is not appropriate).
Embryology is the science of embryonic development, so the answer is not appropriate 4.
The correct answer is: 3.
Physiology answers the question: "How does it work?"
REFLEX - the work of the body (response to ...)