The twins at birth do not know each other .A. separatedB. being separatedC. having separat

问题补充：

The twins,at birth,do not know each other .

A. separated

B. being separated

C. having separated

D. having been separated

答案：

(答案→)A. separated

B. being separated

C. having separated

D. having been separated

解析：分词的完成时(一般作状语)在句中一般不可作定语。如果要作定语，只能用定语从句who have been separated 。所以不选D.