His teacher told him that since his parents were working abroad , either his grandparents or one of his uncles ______ allowed to come to the parents’ meeting .

A．was

B．were

C．are

D．is

对负荷试运行人员的基本要求有：培训已完成，各工种人员经考试合格，取得上岗证，达到( )。

A．三懂四会

B．四懂三会

C．三懂六会

D．三查四定