Passenger volume in the airline industry has declined dramatically over the past two years, and thus fewer travelers and fewer planes are using airports. Since airport expansion can be warranted only by increases in air traffic volume, and since it will probably be at least five years before passenger volume returns to and then exceeds its previous level, it seems surprising that now is the time that airports are going ahead with plans to expand their passenger terminal facilities. Which one of the following, if true, provides the best reason in favor of the airports' timing of their planned expansions? ['When passenger volume begins to grow again after a period of decline, most airlines can, initially, absorb the increase without adding new routes or new planes.', 'A sustained decline in passenger travel could lead to the failure of many airlines and the absorption of their routes by those airlines that survive.', 'It is generally more difficult to finance major construction projects when the economy is in a period of decline.', 'Low volume in passenger air travel permits airport expansion with relatively little inconvenience to the public.']