An unidentified wit once said, "laugh, and the world laughs with you. Snore, and you sleep alone." Yet snoring is far from a laughing matter, as those unfortunates with good hearing, who are rightly subjected to the sounds of the snoring disorder, will testify.
　　
　　It has been estimated that one of eight Americans snores; this means that there are approximately 21 million people --- women as well as men - who render an unpleasant sound when they are asleep. And assuming that each snorer disturbs the sleep of at least one other person, it necessarily follows that there are 21 million unhappy listeners. While a sleeping person breathes, either in or out, several structures in his nose and throat generate the snoring. The sounds, coming from the soft palate and other soft structures of the throat, are caused by vibratory responses to inflowing and outflowing air. When the soft tissues of the mouth and throat come close to the lining of the throat, the vibrations that occur are caused by the position of the tongue. In short, the noise made by snoring can be compared to the noise when breezes flutter a flag on a pole. The frequency of the vibrations depends on the size, density, and elasticity of the affected tissues and on the force of the air flow. Although it is usually the process of in haling or exhaling through the mouth that cause snoring, short snores come from the nose of an open-mouthed sleeper. In all fairness to snorers, however, it should be emphasized that snoring is an involuntary out which stops as the offender is awakened.
　　
　16. If each snorer disturbs the sleep of one other person,the number of Americans that are unfortunately subjected the sound of the snores will be _____.
　　 [A] one out of five
　　 [B] one out of eight
　　 [C] eight out of one hundred
　　 [D] one out of eighteen

　17. The snoring is caused by _____.
　　 [A] the soft palate and other structures of the throat
　　 [B] the inflwoing and outflwoing air through the nose
　　 [C] the inflowing and outflowing air throught mouth
　　 [D] the vibrations as a result of the inflwoing and outflowing air

　18. If a person produces short snores,most probably he has _____.
　　 [A] a soft palate
　　 [B] a big nose
　　 [C] an open mouth
　　 [D] a small throat

　19. Which of the following statements is true?
　　 [A] The snorers can have control over their act.
　　 [B] Both the listeners and the snorers wish to stop the offensive sound of snoring.
　　 [C] The frequency of the vibrations depends on the position of the tongue.
　　 [D] There are more men than women who snore.

　20. The author's attitude towards the snorers is _____.
　　 [A] objective
　　 [B] subjective
　　 [C] sympathetic
　　 [D] annoyed