People expect that ______. A: the airliners of today would eventually be replaced by helicopters B: helicopters would someday be able to transport large number of people from place to place as airliners are now doing C: the imaginations fired by the Russian engineer's invention would become a reality in the future D: their fantastic expectations about helicopters could be fulfilled by airliners of today

According to the passage, people expect that______. A: helicopters could eventually replace the airliners of today B: their imaginations fired by the Russian engineer's invention would be realized in the future C: their fantastic expectations about helicopters could be fulfilled by airliners of today D: helicopters would someday be able to carry millions of people from place to place as airliners are now doing

词汇与结构 For balloons, helicopters and some specialized fixed-wing aircraft, no _______ is needed.