什么情况用more和most

　　Most of the problems were due to human error.

　　多数问题都是人为错误造成的。

　　Most of the people on the course were professional women.

　　参加本课程的大多数人是职业女性。

　　She tried to be more positive about her new job.

　　她力求对新工作更有信心。