A、Good looks. B、Clever brains. C、Sweet personality. D、Willingness to serve. D短文开头提到looks，Brains和personality在空乘工作中都不是最重要的条件。随后提到a

It takes more than good looks to be an air hostess. Brains will help but they are not the main thing. Neither is personality, nor the skill alone. Rather it is a combination of these factors that makes the ideal air girl. And above all she must be willing to serve. This adds up to a pretty tall order, hence so few are chosen from the many who answer the requirement.
    One newspaper advertisement inserted by Japan Air Lines recently attracted five hundred applicants. Only twenty were selected.
    The hostess applicants must not be younger than twenty or older than twenty-eight. They must have a good secondary school education. They ought to be attractive, in good health, speak English and at least two other languages and they must be single.
    If the girls do their job well, it is because of proper training. They learn to prepare and serve meals, and how to take care of children. They must know how to work out the price of a packet of cigarettes in three currencies; know how to pour coffee for four and not spill a drop. They must also know something about the theory of flying and the parts of an aircraft in detail.
    Says an air hostess: "I love my job, of course, for I love traveling, playing golf and tennis. I swim, ride horses, row boats, cycle and roller skate. I love the air and the air-traveling business. It’s simply exciting! "
Questions 16 to 19 are based on the passage you have just heard.
16. What is the essential trait for an ideal air hostess?
17. What can we learn about air hostesses from the passage?
18. Why can they do their job well?
19. What is the passage mainly about?