Back in the old west, it could take over a month to get a letter from the east out to the west coast. people got tired of waiting. so two businessmen decided to set up the pony express, a kind of relay race on horseback from missouri to california. with the pony express, the mail got all the way to california in only ten days! the structure of the selection above can best be described as a) definition. b) sequence. c) compare and contrast. d) cause and effect.