Me will gibe best answer
the vice president which means that no senator addresses the senate floor without formal recognition from the vice president (or president pro tempore). he also enforces and often interprets the rules and procedures of the senate.
a. presides over the senate
b. always leads debate in the senate
c. endorses one side of the senate debate
d. decides the winners and losers in senate debates

The answer to your question would be b

The constant presence of diseases or infectious agents within a given geographic area or population group. it may also refer to the usual prevalence of a given disease with such area or group. it includes holoendemic and hyperendemic diseases. a holoendemic disease is one for which a high prevalent level of infection begins early in life and affects most of the child population, leading to a state of equilibrium such that the adult population shows evidence of the disease much less commonly than do children (malaria in many communities is a holoendemic disease). a hyperendemic disease is one that is constantly present at a high incidence and/or prevalence rate and affects all groups equally. so probably family history.

(d) it was complex and capable of highly organized efforts.