Gigantic passenger planes currently being developed will have enough space to hold shops and lounges in addition to passenger seating. However, the additional space will more likely be used for more passenger seating. The number of passengers flying the air-traffic system is expected to triple within 20 years, and it will be impossible for airports to accommodate enough normal-sized jet planes to carry that many passengers. Which one of the following most accurately states the conclusion drawn in the argument? ['Gigantic planes currently being developed will have enough space in them to hold shops and lounges as well as passenger seating.', 'The additional space in the gigantic planes currently being developed is more likely to be filled with passenger seating than with shops and lounges.', 'The number of passengers flying the air-traffic system is expected to triple within 20 years.', 'In 20 years, it will be impossible for airports to accommodate enough normal-sized planes to carry the number of passengers that are expected to be flying then.']