The sign says that children are admitted only if by an adult.A. to be accompanied　B. acco

问题补充：

The sign says that children are admitted only if by an adult.

A. to be accompanied

B. accompanying

C. accompanied

D. to accompany

答案：

A. to be accompanied

B. accompanying

(答案→)C. accompanied

D. to accompany

解析：句意：牌子上写着，儿童必须有成年人陪同方可入场。这里其实是状语从句的省略，省略了children are或they are。accompany与children之间是动宾关系，所以应用v.­ed形式。