It is a mystery that has puzzled doctors for decades. But experts believe they h

It is a mystery that has puzzled doctorsfor decades. But experts believe they have now finally solved the trickyquestion of why winter is notoriously known as the flu season.

According to a new research, the influenzavirus coats itself in a protective fatty shield that is tough enough to resistcold temperatures. The butter-like material only melts when it hits therespiratory tract（呼吸道）, leaving the virus free to infect cells-- a process scientists sayis like an M&M melting in the mouth.

However, in warmer outdoor temperatures,the protective coating melts before it reaches a person or an animal, killingthe bacteria before they can infect someone. Joshua Zimmerberg, from theNational Institute of Child Health and Human Development (NICHD), in the US,which led the study, said: “Like an M&M in your mouth, the protectivecovering melts when it enters the respiratory tract. It's only in this liquidperiod that the virus is able to enter a cell to infect it.”

In the past, scientists worked on theoriesthat flu is more common in winter because people spend more time inside or theradiation from the sun in summer kills off germs. But no research successfullyexplained the spread of the disease.

Researchers have already claimed that thereport, which is published in the journal Nature Chemical Biology, could leadto new ways to prevent and treat flu. “Now that we understand how the flu virusprotects itself so that it can spread from person to person, we can work onways to prevent it.”

Influenza and other respiratory viruses arespread in small drops broadcast by coughing, sneezing and talking and which canalso settle onto surfaces, to be picked up on fingertips.

1. What can be the best title of thepassage?

  A. The mystery that has puzzleddoctors for decades.    B. New ways to prevent and treat flu.

  C. A discovery of how flu strikes inWinter.            D.Ways found to prevent flu.

2. Which of the following statements is NOTtrue?

  A. Doctors have been trying hard todiscover why flu strikes in winter.

  B. In the past, scientists didn’tknow how flu spreads.

  C. It is possible that flu viruswill no longer threaten humans in winter.

  D. People get affected by flubecause they spend much more time inside in winter.

3. Where should you insert the followingparagraph into the passage?

Duane Alexander, the director of NICHD,said: “The study results open new avenues of research for thwarting (使…受挫)winter flu outbreaks.”

  A. Between Paragraphs 1 and2.     B. Between Paragraphs 3 and 4. 

  C. Between Paragraphs 4 and5.     D. Between the last two paragraphs.

4.In what process or order does flu occur?

  a. The virus infectscells                b. The influenza virus was born

  c. The butter-like materialmelts           d. The virushits respiratory tract

  e. The virus coats itself inbutter-like shield  f. The virus is free

  A. a, c, d, e, b, f.     B. c, f, d, b, e, a.    C. b, e, d, c,f, a.    D. d, b, e, c, f, a.

试题答案

【答案】

 C

 D

 D

 C

【解析】