Answer:
it's so that it can provide energy for the animals that needs to eat the food to live and also to provide oxygen.
I'm pretty sure its A. but i'm not 100% sure. But I hope this is correct!
Hope this helps. :)
The possible blood types<span> are: O+, O-, A+, A-, B+, B-, AB+ and AB-. O+ is the most common blood type. AB- is the rarest blood type.
Hope this helps :-)</span>