Which of these best describes the role and mechanism of action of Cyclin-dependent kinases (CDKs) in the cell cycle?

The correct option is D

All of the above

Cyclin-dependent kinases (CDKs) are a family of protein kinases first discovered for their role in regulating the cell cycle. A cyclin-dependent kinase complex (CDKC, cyclin-CDK) is a protein complex formed by the association of an inactive catalytic subunit of a protein kinase, cyclin-dependent kinase (CDK), with a regulatory subunit, cyclin. Once cyclin-dependent kinases bind to cyclin, the formed complex is in an activated state. Through phosphorylation, CDKs signal the cell that it is ready to pass into the next stage of the cell cycle.