For call options, the options holder can demand that the options seller sell shares of the underlying stock at the strike price. (investopedia.com)
Conversely, when you sell a call option, you must sell shares of the underlying stock at the specified price when the option is exercised. (creditdonkey.com)
When either of these types of equity options is exercised, a physical delivery of shares of its underlying stock from one party to another takes place. (education.optionseducation.org)