By definition, the number
is the ratio between the circumference and the diameter:

This implies that

And so your circumference is 
Answer:
D. All of the above
Step-by-step explanation:
A is right, 3(g) = 3g
I don't know about b, but c is right, so it is all of the above
Answer:
2.83
Step-by-step explanation:
using the pythagorean theorem,
≈
Answer:
(-4,3)
Step-by-step explanation:
hope this helps :)