Professor Amnesius messed up the definition of the following terms. Help the professor associate the

terms with the correct definitions by using numbers and letters. As an example, if you think t is the

correct definition for the term number $10,$ you only need to write $10-$t$.$

$1.$ Instance of a relation

a$.$ a description of the database structure, data types and constraints.

$2.$ Superkey of a relation

b$.$ a tool used to specify actions the database system performs when

certain events and conditions occur.

$5.$ Foreign key of a relation

e$.$ A constraint stating that foreign key values must match a primary key value of some tuple in the

referenced relation or be NULL.

$6.$ Entity integrity

f$.$ a tool used to specify additional types of constraints not covered with built$-$in constraints.

$7.$ Referential integrity

g$.$ A constraint stating that in a base relation no attribute of a primary key can be null.

$8.$ Database Schema

h$.$ the relation with all its tuples written out represents an instance.