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A. Main Results of Recent Researches

B. Difference between Genetic and Observed Intelligence

C. Effect of Environment on Intelligence

D. Intelligence and Achievement

E. Impact on School Education

F. A Changed View of Intelligence

Which of the following is a bad habit of the executive passengers that frustrates the airlines?(  )

• A、They do not book their seats in advance.
• B、They do not sit on the seats they are supposed to take.
• C、They do not travel on the flight they have booked.
• D、They do not pay in advance for the seats they book.

According to the passage, in operating airlines it is essential to     .(  )

• A、keep in mind the need. of the executives only
• B、satisfy the need of the low fare passengers at the expense of the executives
• C、try to attract as many passengers as possible by reducing fares
• D、cater to the need of passengers setting at both ends of the jets