Use resources to import csv file into BAS. Define resource type as "Lines from file" and set it to "Use each line one time" if you need that behavior. Than just put resource variable in place of URL.
Select "Mix Lines" in the resource, that way all the lines are mixed and thus it will have a random line. Or you can use javascript to mix the array list using function shuffle to get a better constant randomization. I believe there's also the option "Shuffle List" under the "List" option
