Final answer:
The cleavage furrow in a dividing cell is determined by the contractile ring of actin and myosin, which contracts to divide the cell in two.
Step-by-step explanation:
The position of the cleavage furrow in a dividing cell is determined by the contractile ring of actin and myosin filaments. During the process of cytokinesis, this contractile band forms just inside the plasma membrane at the former metaphase plate.
The actin filaments pull the equator of the cell inward, leading to the formation of a fissure known as the cleavage furrow. As the ring contracts, it pulls the plasma membrane with it, which deepens the furrow until the cell is eventually split into two separate cells. Thus, the correct answer to the question is B) Contractile ring of actin and myosin.