People believe that he and a friend discovered tra...

Câu hỏi: People believe that he and a friend discovered traces of treasure in the hole.

A It is believed that he and a friend had discovered traces of treasure in the hole.

B  Traces of treasure are believed to have been discovered in the hole by him and a friend.

C Traces of treasure were believed to have been discovered in the hole by him and a friend.

D It was believed that he and a friend had discovered traces of treasure in the hole.