We can associate a key with each relationship in an E$/$R model.

Let

$$

R be a relationship among entity sets

$$

$1$

$,$

$...$

$,$

$$

$$

E

$1$

$$

$,...,$E

n

$$

$.$

A key for relationship

$$

R is defined as a set

$$

K consisting of attributes chosen from the attributes of

$$

$1$

$,$

$...$

$,$

$$

$$

E

$1$

$$

$,...,$E

n

$$

such that if

$($

$$

$1$

$...$

$,$

$$

$$

$)$

$($a

$1$

$$

$...,$a

n

$$

$)$ and

$($

$$

$1$

$,$

$...$

$,$

$$

$$

$)$

$($b

$1$

$$

$,...,$b

n

$$

$)$ are two different tuples in

$$

R$,$ then these two tuples cannot agree on all the attributes of

$$

K$.$

Consider the following E$/$R diagram. What is the smallest possible set of attributes that can make up the key of

$$

R$?$

$1$ point

A$1,$ A$2,$ A$3,$ A$4,$ A$5,$ A$6,$ A$7,$ A$8,$ A$9,$ A$10,$ A$11,$ A$12$

A$5,$ A$6,$ A$9,$ A$10$

A$1,$ A$2,$ A$3,$ A$5,$ A$6$

A$9,$ A$10$

A$1,$ A$5,$ A$9$