They created the sarcophagus, an elaborate burial container to further preserve the dead
The third statement is correct.
Nick, who was our dorm advisor, and Joe, Nick's roommate, raised their concerns to the school residence office. They wanted to know why Dennis didn't have to share a room.
In the first statement, there are two subjects- Nick and Joe. However, "his" is used in the predicate referring only to one of the two subjects. This made the sentence incorrect. The same with the second statement. It used not only "his" in the first sentence, but it also used "he" in the second sentence referring to only one of the two subjects mentioned, instead of "they".
(A )his rule was to over see the debates
