Their valency is one and both belong to the third period
The Earth was first considered habitable when we discovered that it was Microbial organisms that started the process. I would go with D.
Air pressure (inside the lungs) is lowest when lung volume is highest, so the answer is B. when you breathe in your lungs expand, which makes the air molecules spread out, therefore the pressure is lower.
Parietal and frontal.. whichever one your looking for
