First, they may produce direct and relatively short-lived effects, such as stimulation of the isolated uterus or relaxation of the isolated tracheal chain preparation.
Secondly, in doses too low to produce a direct effect, they may produce a long-term potentiation of the effects of other stimulants.
Answer:
C) Modernization of humans
The formula unit of compound made up from Pb4+ and oxygen is PbO2.