Final answer:
The abbreviation for the U.S. coding system that classifies businesses by operations is 'c. SIC', which stands for Standard Industrial Classification.
Step-by-step explanation:
The abbreviation for the U.S. government coding system that classifies a firm by its specific type of business operations is c. SIC, which stands for Standard Industrial Classification. This system is used to categorize businesses by the type of economic activity they engage in. The other options listed, such as NASDAQ (National Association of Securities Dealers Automated Quotations) and NYSE (New York Stock Exchange), refer to stock exchanges where securities are traded, while SEC (Securities and Exchange Commission) is the regulatory body that oversees the securities industry and stock market.