What is the primary source of debt capital for existing businesses?

A) Commercial banks
B) Government programs
C) Non-financial companies
D) Brokerage firms

Commercial banks are the primary source of debt capital for existing businesses. They provide loans and credit lines for various purposes, such as working capital, expansions, and acquisitions. Government programs, non-financial companies, and brokerage firms may also offer debt capital, but they are not typically the primary source for existing businesses.