If Ribonucleotides Were Depleted from a Cell During S Phase

If ribonucleotides were depleted from a cell during S phase, how would DNA synthesis be affected? (Ignore energetic considerations.)

A) There would be no effect because ribonucleotides are used in RNA synthesis, not DNA synthesis.
B) DNA synthesis would continue but at a slower rate.
C) There would only be an effect during M phase, not in S phase.
D) DNA synthesis would not be affected because ribonucleotides are only used during the process of transcription.
E) Replication would cease because ribonucleotides are required to initiate DNA synthesis.