Answer:
1=A population is the number of living people that live together in the same place.
2=July 11th,1897 is famous for world population day.
3=A census is the producer of systematically enumerating and acquiring and recording information about the member of a given population .
4=The reason behind decreasing trend of population was worldwide influenza epidemic Famine ,unscientific census and heavy casualties suffered by NEPALIES ARMY in the first worldwide war.
5=Census and administrative records are the two primary sources of population data.