Please also mention the phases in which these events occur

Dear Student, The answer of given question is option (a) because Nucleotide Synthesis starts in G1 phase, then the histone protein starts in S phase, Tubulin synthesis occurs in G2 phase and centromere splitting occurs in Anaphase ( part of M phase) of cell cycle. The order of cell cycle is G1 (Gap-1) phase, S(Synthesis) phase, G2 (Gap-2) phase and at last M phase. Regards