The correct answers are "mutual fund", "money market", "real state", and "Stock".
All of these are forms of investment with varying volatility and there, risk.
<em>Mutual Funds</em> are a form of investment in which you save you entrust your money to an institution who promises you a given return by investing it in diverse markets.
The <em>Money Market</em> is also an option for trading financial instruments with usual high rates of return (and risk).
<em>Real Estate</em> investments are an expensive, yet very safe way of investing, as land is the only asset which does not depreciate or lose value.
<em>Stocks</em> are a small percentage of ownership of companies. The expectation is that the value of these companies will rise leading to a potential gain by selling the stocks.