Rb is an important protein in human disease. If there is a mutation in Rb so that it cannot be phosphorylated by Cdk2, what would result?

a) Inhibition of the transcription of proteins involved in DNA replication
b) Loss of function of the G1 checkpoint to give unregulated progression through the cell cycle
c) Increased levels of p53 and p21
d) Uncontrolled ubiquitylation of securin
e) Unregulated activity of the Cdk2/Cyclin E complex