Answer:
C is a function
Explanation:
for a relation to be a function each value of x must map to exactly one unique value of y
A
2 → 5 and 2 → 2 ← not a function
B
- 1 → 6 and - 1 → 7 ← not a function
C
all values of x map to exactly one unique y ← function
D
3 → 1 and 3 → 2 ← not a function