Whaaat.. I don’t understand that language..
It's called merging cells. I don't understand why this is in Biology but whatever.
For the answer to the question above, oxygen makes it Redi would think it has to do with the amount of oxygen in the blood stream. So the answer is the third one, t<span>he presence of oxygen–bound hemoglobin makes it bright red.
I hope my answer helped you</span>
