In a
call option, to
buy the
underlying asset. The
option holder has no obligation to call the option and only does so if he/she believes it benefits him/her. Depending upon the nature of the option, this may be done at any point during the life of the contract, or it may only be done on the contract's
expiry date. The
strike price of the sale is agreed upon in the option contract (that is, before the option is exercised).