What caused the end of pony express?

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.