Final answer:
Cdk inhibitor proteins bind to the active Cdk complex, prevent phosphorylation of the target, and delay G1 to S progression.
Step-by-step explanation:
The molecule that binds to the active Cdk complex, prevents phosphorylation of the target, and delays G1 to S progression is Cdk inhibitor proteins. These proteins block the progression of the cell cycle by preventing the full activation of Cdks. Many Cdk inhibitor molecules monitor specific cell cycle events and remove the block on Cdks only when those events are completed.