The correct answer is: There are 20 primary teeth, and by 24 months of age most children have all 20.
Primary teeth also known as deciduous teeth, milk teeth, are the first set of temporary teeth in the growth development of humans. They develop during the embryonic stage of development, become visible in the mouth during infancy (erupt) and usually get replaced by permanent teeth around age six (the first tooth). The primary teeth consist of 4 central incisors (one in each quadrant), 4 lateral incisors, 4 canines, 4 first molars, and 4 secondary molars.
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).
