听力原文：It's no secret that throughout history common stock has outperformed most financi

听力原文： It's no secret that throughout history common stock has outperformed most financial instruments. If an investor plans to have an investment for a long period of time, then their portfolio should be comprised mostly of stocks ; however, investors who don't have this kind of time should diversify their portfolios. For this reason, the concept of "asset allocation" was developed. Asset allocation is an investment portfolio technique that aims to balance risk and create diversification by dividing assets among major categories. The underlying principle of asset allocation is that the older a person gets, the less risk he or she should face. After you retire you may have to depend on your savings as your only source of income.

28. Throughout history, what kind of stock has outperformed most financial instruments？

29.What is the purpose of asset allocation？

30.What is the principle underlying the concept of asset allocation？

(28)

A．preferred stock

B．common stock

C．concept stock

D．cynical stock