In the context of control of the cell cycle, what is the primary role of cyclins in a cell?

• A. They function as membrane channels that control ion flux to trigger cytokinesis.
• B. They bind to and activate cyclin-dependent kinases (CDKs) to regulate progression through specific cell-cycle phases.
• C. They form the structural scaffold of the mitotic spindle to separate sister chromatids.
• D. They act as DNA polymerases that replicate the genome during S phase.

Answer: (B)