Which of the following statements best describes what a so-called patent troll is ________.
1) A person or company that enforces patent rights aggressively and often with questionable legal tactics
2) A person or company that holds patents but does not manufacture or sell any products
3) A person or company that buys patents solely for the purpose of suing others for infringement
4) A person or company that uses patents to stifle competition and hinder innovation