What body systems that are most directly responsible for delivering oxygen to an animal's cells

The second one is the answer edg.

Boreal forest another word for this is taiga.but it is a biomes, that stretches across the northern regions of north america, europe, and asia.~ hope this ! (if this is correct may i have brainy? )

It's probably because the earth is actually tilted and is not straight when orbiting the sun. that's why when it's winter here, it's summer in the southern hemisphere. in the wintertime in the northern hemisphere, it's colder here because it's tilted away from the sun and the southern hemisphere is tilted closer to the sun (i believe this is the case anyways)