【名词&注释】
劳动合同订立(concluding labor contract)、具体要求(concrete requirements)、有关规定(related regulations)、承担责任(undertake responsibility)、劳动合同履行(executionof labor contract)
[单选题]劳动关系建立之日是().
A. A.劳动合同订立之日B.劳动合同履行(executionof labor contract)之日C.实际用工之日D.劳动合同双方签字之日