Answer:
Option C
Step-by-step explanation:
A function's input is assigned to exactly one output. Any input must not repeat.
Option A's not a function because the input of 3 repeats.
Option B's not a function because the input of -4 repeats.
Option C's a function because no inputs repeat.
Option D's not a function because the input of 5 repeats.
Hope this helps.
