五、解釋 super key、candidate key、primary key 與 foreign key；並繪圖表示四者之間的關係。（15 分）

⑴Hillary Clinton gives Obama total backing. Hillary Clinton made an emphatic plea for Democrats to unite behind the presidential candidacy of Senator Barack Obama, exhorting her supporters to back her one-time rival because victory over Republican Senator John McCain “is a fight for the future and a fight we must win together.”