Given the following relations:

Book $($ISBN$,$ name, author, publisher, number of pages, library$)$

Library is a foreign key referring to 'zip code' in 'Library'. This value can be NULL.

Library $($zip code, straat, nr$,$ city, opening hours$)$

Customer $($ID$,$ name, date of birth$)$

Loan $($ISBN$,$ customerID$)$

ISBN is a foreign key referring to 'ISBN' in 'Book' and cannot be NULL.

customerID is a foreign key referring to $\text{'}$ID$\text{'}$ in 'Customer' and cannot be NULL.

Which statement is not correct?

Group of answer choices

A book can be loaned by different customers.

All the relations are in $2$NF but not in $3$NF$.$

A library can be uniquely identified based on its zip code.

A customer can loan multiple books.