问题如下：
Which of the following statements is most correct?
选项：
A. When market price goes down, putable shares are more risky than callable shares for investors.
B. When market price goes up, callable shares are more risky than putable shares for investors.
C. When market price changes, non-putable, non-callable shares are the most risky for investors.
解释：
B is correct.
When market price rises, the firm has option to buy back the shares , therefore investors have limited gains when they hold the callable shares. When market price drops, investors can sell the shares back to the firm, therefore investors have protection when they hold the putable shares.
价格上升时，公司为什么会以低价再回购股票呀？应该是价格下降吧？
