Suppose a book author can be identified by an AuthorID and each book can be identified by an ISBN. Besides the identifier, an author and a book each has many other attributes like name, address, email, phone, and price, title, publisher, publish year, edition, etc. In general publishing business, an author may write no book or many books but every book must have at least one author.

a) We know that atleast one or more author writes a book.

Symbol to indicate one or more is (B)

So the correct option is B

b) We know that zero to multiple books are written by any author.

Symbol to indicate zero or more is (A)

So the correct option is A

c) The fourth option is correct if we replace by many to many relationship and generate a new entity.

So the relationship betweem author and contract is one to many. So we know that there is atleast one author that represent in symbol d and books has atleast 0 that represent in symbol c.

So Fourth Option is correct d at blue side and c at red side.

d) There are two forirgn keys in table Contract one is from AuthorId and other is ISBN.

So correcct option is C

b. xor is the correct answer

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