Chapter 06 continues with design. Select on of the following short-answer questions and answer it. You should then provide a short example of your answer -- minimum 3 sentences. ____________________ key restrictions determine the relationships between tables. ____________________ refers to the number of items that must be included in a relationship. A relationship that is not necessary for identification is called a(n) ____________________ relationship. A weak entity corresponds to the term ____________________. A(n) ____________________ is a special value that represents the absence of a value in a field. You can recognize entity subtypes by the fact the primary key is also a(n) ____________________. One way to indicate a one-to-many relationship is to place a crow's foot at the ____________________ end of the relationship. Your subject line should indicate which short answer your are working by number.