The answer is Eukaryotes.
Answer:
Sonography
Explanation:
sonography is an ultrasound, which is what most people are used to hearing.
Nitrification. The conversion of ammonium to nitrate is performed primarily by soil-living bacteria and other nitrifying bacteria. In the primary stage of nitrification, the oxidation of ammonium ( NH+4) is performed by bacteria such as the Nitrosomonas species, which converts ammonia to nitrites ( NO−2).
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.
