The school rule states that no child shall be, unless______by an adult, allowed out of the school during the day.
A.was accompaniedB.accompanyingC.accompaniedD.being accompanied在线课程C
解析：
考查从句的省略式：unless accompanied=unless the child is accompanied by an adult，句意是：学校规定说，没有孩子在没有成人的陪伴下可以在白天出学校。选C。