Could you explain why those choice are the right answers and other ones are wrong?

Which of the following is true with respect to databases? Selectall that apply.We cannot join tables unless a primary key / foreign keyrelationship has been specified between them.Correct!VValidation rules help prevent erroneous data entry by defining therequirements for a valid entry.Correct AnswerUser profiles define what actions a user can take within adatabase, including which tables they can view and which theycan edit.You AnsweredVA primary key must be a single field that uniquely identifies eachrecord.