The simple circular flow model shows that
a. total income received by households is different from the dollar value of all goods and services produced because the units of measurement are not the same.
b. total income received by households is less than the total value of goods and services produced because of leakages.
c. total income received by households is less than total payments to business because there are business profits.
d. total income received by households must be equal to the dollar value of all goods and services produced.

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?