Final answer:
Money Market Mutual Funds invest in short-term, high-quality instruments such as Commercial Paper, Repurchase Agreements, and Treasury Bills, but not in Corporate Bonds, which are long-term and part of capital markets.
Step-by-step explanation:
Money Market Mutual Funds typically invest in short-term, high-quality, and liquid financial instruments. These funds aim to provide investors with a safe place to invest easily accessible, cash-equivalent assets. The instruments in which these funds invest often include Commercial Paper, which is an unsecured, short-term debt instrument issued by a corporation, Repurchase Agreements (often called repos), which are short-term borrowing for dealers in government securities, and Treasury Bills (T-Bills), which are short-term government securities with maturity periods of one year or less.
However, Money Market Mutual Funds generally do not invest in Corporate Bonds because these are typically long-term investments with maturities greater than one year, classifying them within capital markets rather than money markets. Therefore, option B 'Corporate Bonds' is the correct answer as it is the one that Money Market Mutual Funds do not invest in.