A. It has mass.
Air is matter, and can't be seen thus not all matter can be seen.
Any liquid or gaseous is matter (water, air, etc.)
Since it can be liquid or gaseous it doesn't have to maintain it's shape and size to be matter.
Nitrogen is a major component by which plants use sun energy to produce sugars from water and carbon dioxide. (It is also a major component of amino acids)
Answer:
The decline rate ranges from 2.7 to 3.79
Answer:
O Cells are all the same on the inside