请教老师这道题可以用european put option公式来考虑吗？

问题如下：

The value of a European put option can be either directly or inversely related to the:

选项：

A.

exercise price.

B.

time to expiration.

C.

volatility of the underlying.

解释：

B is correct.

The value of a European put option can be either directly or r inversely related to time to expiration. The direct effect is more common, but the inverse effect can prevail the longer the time to expiration, the higher the risk-free rate, and the deeper in the- money is the put. The value of a European put option is directly related to the exercise price and the volatility of the underlying.

中文解析：

欧式看跌期权的价值跟Time to expiration的关系可能是positive，也有可能是negative的。

因为看跌期权的收益是有限的（股价最低跌到0），当在到期之前期权是deep in the money，此时又不能提前行权，只能焦急等待赶快到期行权。此时距离到期时间越长，对投资者越不利。