The small T antigen of SV40 regulates the cell cycle of the host cell by DIRECTLY doing which of the following?

A) Turning on transcription of cyclin D1.
B) Turning on the activity of the MAP kinase.
C) Inhibiting the activity of the PP2A phosphatase.
D) Phosphorylating the transcription factor AP1.
E) Inactivating the p53 protein.