In One Type of a Lookback Option

In one type of a lookback option,

A) You can decide to change the option from a call to a put or vice versa at the last minute.
B) You can take any observed price prior to maturity as the strike of the option.
C) You can take the average observed price of the underlying in determining the option payoff.
D) The initial price of the underlying acts as the strike price of the option.