Vansen left for school at $6:30$ am. He took half an hour to walk from his house to school. Ron reached school $1$ hour later than Vansen. At what time did Ron reach school? (adapted from 2009 Math Kangaroo Problem, Level 3-4, Question \#8) 
选项为:A:$7:00$ am.  B:$8:00$ am.  C:$8:45$ am.  D:$9:00$ am.  E:$10:00$ am.  请回答其中一个选项.