Answer: A) I only
Step-by-step explanation:
Relation I has each item in the domain map to exactly one item in the range. So any input leads to exactly one output. Therefore, we have a function here.
In contrast, relation II has the input x = 0 lead to multiple outputs (namely y = 8 and y = -1 at the same time). This indicates we do not have a function here.
Relation III is the same as as the previous one. This time the input x = -2 maps to both y = 1 and y = -7 at the same time. We don't have a function here either.
If you wanted, you can plot these points on the xy plane to see that relations II and III fail the vertical line test. You would need to plot each relation separately.