Final answer:
Cyclin-dependent kinase 2 (CDK2) is activated by cyclin E to progress the cell cycle from G1 phase to S phase.
Step-by-step explanation:
To activate cyclin-dependent kinase 2 (CDK2), it must bind to and be activated by cyclin E. Cyclin E forms a complex with CDK2, and this complex is necessary for the progression of the cell cycle from the G1 phase to the S phase. Cyclin E-CDK2 complex plays a crucial role in regulating the initiation of DNA synthesis and the transition of the cell cycle.