I think the answer is letter B
Wrong,
You added when you were supposed to divide.
24/30 = 0.8
The formula for the radius is

so the answer would be 6 inches
Answer:
B
Step-by-step explanation:
The best - well, only way- is to check a few points.
Namely -1 (unless your eyesight is really poor!), 0, 1, 2, and 3.

Now you can mark all these points in each graph (well, you could if they were on paper and not on a screen) and see which one of the lines passes through all of them. Spoiler alert, it's the B graph.
A represents
, B is the one you want, C is
and D looks like 
Answer: 18 ft per second
Step-by-step explanation: 36 divided by 2