The answer here is D, and it's kind of obvious. But you probably already knew the answer and are just doing this for piece of mind.
Explanation: Just the fact that we don't know whether or not there even is extraterrestrial life rules out every other answer, without even needing to go in depth.
(Okay, I read your question completely wrong, it's asking for which one of these has been solved isn't it?)
This is tough because all of these other than D have been figured out. Go with the methane atmosphere then.
Answer:
Increase EDV and therefore, increase stroke volume.
Explanation:
EDV is the volume of blood which filled the ventricle before its contraction while ESV is the volume of blood remain in ventricle after ejection.
When venous return increases, this will increase the pressure on ventricle contraction which can lead to eject of addition blood returned to it.
So, increase in EDV results in an increase of stroke volume (SV).
Answer:
A.? i'm not 100% sure tho
Explanation:
