血培养皮肤消毒的“三步法”是指（）

A.75%乙醇30s,10%碘伏60s,75%乙醇60s(正确答案)

B.10%碘伏60s,75%乙醇30s,75%乙醇30s

C.75%乙醇30s,75%乙醇30s,10%碘伏60s

D.异丙醇30s,75%乙醇60s,75%乙醇30s