Answer : 2. "Cell biology"
Explanation :

Answer: B) Cell biology Explanation: The branch of biology that studies the different structures and functions of the cell is called Cell Biology or Cytology.    A cell is the smallest unit of life that can replicate independently, and cells are often called the "building blocks of life"    Cell Biology deals with : Life cycle  Structure and organisation of cell organelles and their physiological properties.  Metabolic processes  Interactions with their environment  Signalling pathways.