In 1914, the united states prohibited the importation of mexican avocados even though mexico is the world's largest producer of the fruit. this prohibition remained in effect until 1996. the ban on importing mexican avocados is an example of a(n):

Google started as one of many internet search engines, amazon started as an online book seller, and ebay began as a site where people could sell used personal items in auctions. these firms have grown to be so large and dominant that they are facing antitrust scrutiny from competition regulators in the us and elsewhere. did these online giants grow by fairly beating competition, or did they use unfair advantages? are there any clouds on the horizon for these firms -- could they face diseconomies of scale or diseconomies of scope as they continue to grow? if so, what factors may limit their continued growth?