Answer:
all of them
Explanation:
dogs per Good Boy treats Probably this would work better the other way around.
good boy treats / dog
Both could be considered correct.
number of chocolates per bag. Certainly that's a good ratio, valuable to know if you like chocolates.
people / math this two likely works better the other way around math / people.
Whenever you have two different units and they are separated by a per, then you have a viable ratio.
If you have a sticky teacher and D is not correct, you could try B
See comments below.