As early humans moved into river valleys, what were some of the contributing factors that contributed to epidemics? (check all that apply)

Plz which of the following statements is the best definition of a blockade? a. a blockade is a group of soldiers recruited from a foreign country who serve for the money. b. a block it is a military tactic in which one army moves into place to face another army. c. a blockade is a wooden fence built to defend a colonial settlement. d. blockage is the shutting off of a port by ships to keep people or supplies from moving in or out.