Which of the following is not one of the eight basic puzzles about financial structure？

A、Stocks are the most important source of finance for American businesses

B、Issuing marketable securities is not the primary way businesses finance their operations

C、Indirect finance, which involves the activities of financial intermediaries, is many times more important than direct finance, in which businesses raise funds directly from lenders in financial markets

D、Banks are the most important source of external funds to finance businesses