It’s B I hope this helps :)
Answer:
6b
Step-by-step explanation:
Number 6 is B because each input or x value has one output or y value
Number 7 is C because that’s not even an equation
Number 8 is D because each input or x value has one output or y value
Number 10 is A because if you graph it all of the points would be on a line increasing proportionally
(Hopefully this made sense I tried my best)