A. The R point occurs around 8 hrs after PBS (phosphatebuffered saline) addition. False Exposure to PBS does not induce thymidine uptake. The lack of growth factors fails to support cyclin D synthesis and the consequent R point transition.

B. The R point occurs around 8 hrs after CS addition. True

C. Even after short periods of CS stimulation some cells are capable of some degree of DNA synthesis. True

D. 48 hrs of serum starvation are not sufficient to arrest the majority of the cells in G0. False The results obtained following PBS stimulation indicate that the cells were arrested in G0.