单项选择题
Sub-contractorsshouldobeythecontractorininformationsystemproject.Whencensoringsub-contractors,thesupervisormostlyconcernsabout______.
A．Amountofsubcontract
B．qualificationsandabilitiesofsub-contractors
C．responsibilitiesandobligationsofsub-contractors
D．thecontentsofthesubcontract