China internet giant Tencent Holdings Ltd (0700.HK) share price plunged from above HK$150 to HK$127.40 after its major shareholder Ma Huateng disclosed that he had reduced his stake in Tencent by 5 million shares at $102.70.

His disposal of Tencent shares at such a low price was actually committed last June when Tencent share price was between $83 and $96.  Ma had then entered into a contract which involved him implementing a collar option strategy.  A collar option strategy involves simultaneously buying lower strike price put option and selling higher strike price call option while holding the underlying share.  Both the call and put options are out-of-money.  This strategy limits the upside gain of the share but protect the holder from a sharp fall in share price.  The below diagram depicts the payoff of a collar option strategy.

因墨西哥湾漏油事件而陷入困境的英国石油公司(BP)在有分析家大胆预测或它许会在倒闭后股价暴跌并在上周三6月9日创下最低29美元的股价。这使得在今年4月中还以60美元左右交易的BP在短短两个月内市值少了一半。许多投资者更打赌该公司将在近期内倒闭而买进BP极度价外的认沽期权，使得BP期权和凭单的引伸波幅大增至超过100%水平。这种情况已经和雷曼兄弟事件爆发时的情况一样。BP倒不倒台这个问题相信是很难答的。但是身为投资者我们却有几项投资策略可以采用来从这种情况中获利。