Which statement about the cell cycle control system is FALSE?

There are several checkpoints throughout the cell cycle, where goahead signals must be received before the cycle can continue.

Once bound by cyclins, Cdks become active immediately. So the Cdks usually have their cyclin$-$binding domains blocked by inhibitors until a go$-$ahead signal is received.

The amounts of cyclins in the cell change in a cyclic manner during the cell cycle. The amounts of Cdks stay relatively constant, but their activity levels rise and fall in response to the levels of their partner cyclins.

Cyclin$-$dependent kinases $($Cdks$)$ activate other proteins to carry out the many processes of the cell cycle.