Airport official: Local residents have been complaining that night flights into Plainsville airport disturb their sleep and should be sharply reduced in number. This complaint is completely unreasonable-there have been night flights coming into the airport from the very beginning, twenty years ago, and these residents should have taken that fact into account when buying their homes. Which of the following is an assumption on which the airport argument depends? ['The residents who are complaining have been in their current homes fewer than twenty years.', 'There are fewer night flights now than there were originally.', 'The economic success of the airport depends entirely on the existence of the night flights.', 'The residents who are complaining are ignoring the benefits they gain from the presence of the airport.']