Administration of methotrexate have its' greatest effect on which phase of the cell cycle?

Methotrexate inhibits dihydrofolate reductase preventing the reduction of folic acid to tetrahydrofolate leads to it being the source of 1-carbon in purine nucleotide synthesis and methylation of dUMP to dTMP, Depriving DNA polymerase of essential substrate... is a antimetabolite.. in the S-phase..