Step 1: Understanding the role of stock exchanges.
The primary function of stock exchanges is to provide a platform for the buying and selling of stocks and securities. This facilitates the protection of investors' interests by providing liquidity, transparency, and security.
Step 2: Analyzing the options.
(A) Investor: Correct. The stock exchange ensures that investors have a fair and transparent market to trade, protecting their financial interests.
(B) Company: This is incorrect. The stock exchange is not primarily focused on protecting companies, although it benefits them by providing access to capital.
(C) Government: This is incorrect. The stock exchange's primary function is not to protect the government's interests, although regulation may involve government oversight.
(D) None of these: This is incorrect, as the correct answer is (A) Investor.
Step 3: Conclusion.
The correct answer is (A) Investor, as the stock exchange primarily protects the interests of investors.