Question 1 :
A foreign key is used to implement relationships between tables.
Question 2 :
The terms alternate key and candidate key mean the same thing.
Question 3 :
In 1:N relationships, which entity becomes the parent entity is arbitrary.
Question 4 :
When the parent entity is required, cascading updates and cascading deletions should be allowed or the associated actions on the parent should be prohibited.
Question 5 :
In a 1:1 relationship, the primary key placement is arbitrary.