The correct answer is option 2: Perth-Ankara-Paris-London. This option suggests that the shortest air route from Perth to London involves flying from Perth to Ankara, then to Paris, and finally to London.

Option 1, Perth-Mumbai-Rome-London, and option 4, Perth-Mombasa-Rome-London, both include a stop in Rome before reaching London. However, option 2 is shorter because it skips the additional stop in Mumbai or Mombasa.

Option 3, Perth-Aden-Paris-London, is incorrect because it includes a stop in Aden, which is not on the most direct route between Perth and London.

Therefore, the shortest air route from Perth to London is indeed option 2: Perth-Ankara-Paris-London.