Which statement in the passage should be supported by more specific facts or evidence? A. "Unfortunately, the wall has suffered greatly in recent years from damage and neglect." B. "After conquering and uniting seven warring states, the emperor decided to have the wall built to protect the country." C. "In that time, cannons were inserted along the wall, and watch towers were also added." D. "Its walls are 15 to 30 feet thick and up to 25 feet high."