Which of the following sets of ordered pairs is a functionB
{
(
8
,
1
)
,

(
7
,
0
)
,

(
7
,
−
1
)
,

(
8
,
2
)
}
{
(
8
,
1
)
,

(
7
,
0
)
,

(
7
,
−
1
)
,

(
8
,
2
)
}

C
{
(
6
,
1
)
,

(
7
,
3
)
,

(
4
,
2
)
,

(
6
,
2
)
}
{
(
6
,
1
)
,

(
7
,
3
)
,

(
4
,
2
)
,

(
6
,
2
)
}

D
{
(
1
,
3
)
,

(
2
,
4
)
,

(
−
1
,
−
3
)
,

(
−
2
,
−
4
)