5.蜗杆传动中，齿面在节点处的相对滑动速度vs=__________。 A: vl /siny B: v1/cosy C: v1/tany D: v1tany

Text 3 My interest in Chinese food started years a90，when l was a young reporter for the Washington Post．Our office Wasn’t far from Chinatown，where Ifound some very good Chinese restaurants． The first time I ever ate Chinese food I loved it．I noticed the fresh taste of the meat and vegetables．When I learned more about the food，I beganto understand why it has this special feature． Many years ago，China had an energycrisis(危机)because it lost much of its wood due to over populationand poor management of its forests．This loss was verybad for the country，of course，butit turned out to be very good for the food．Wood becamevery expensive and hard to get，so the Chinese had toeither find a substitute(替代物)for their valuable wood，or learn how to use it better．There weren’tany substitutes so people found ways to—economize． In order to economize in cookin9，they had touse very little wood．So they started cutting their meatand vegetables into small pieces before they put them in the hot oil．That way，the food cooked faster and theysaved their fuel。The food prepared in this way kept its fresh flavor(味道)一and it’s thisflavor that attracts people from other countries to the art of Chinese cooking． According to the text，what makes Chinese food attractive to foreigners（） A: Its way of cooking B: Its long history C: Its special taste D: Its lovely look

Text 3 My interest in Chinese food started years a90，when l was a young reporter for the Washington Post．Our office Wasn’t far from Chinatown，where Ifound some very good Chinese restaurants． The first time I ever ate Chinese food I loved it．I noticed the fresh taste of the meat and vegetables．When I learned more about the food，I beganto understand why it has this special feature． Many years ago，China had an energycrisis(危机)because it lost much of its wood due to over populationand poor management of its forests．This loss was verybad for the country，of course，butit turned out to be very good for the food．Wood becamevery expensive and hard to get，so the Chinese had toeither find a substitute(替代物)for their valuable wood，or learn how to use it better．There weren’tany substitutes so people found ways to—economize． In order to economize in cookin9，they had touse very little wood．So they started cutting their meatand vegetables into small pieces before they put them in the hot oil．That way，the food cooked faster and theysaved their fuel。The food prepared in this way kept its fresh flavor(味道)一and it’s thisflavor that attracts people from other countries to the art of Chinese cooking． The underlined word“economize”in paragraph 3 means（） A: to meet energy crisis B: to find other forms of fuel C: to improve cooking methods D: to use carefully without waste

Text 3 My interest in Chinese food started years a90，when l was a young reporter for the Washington Post．Our office Wasn’t far from Chinatown，where Ifound some very good Chinese restaurants． The first time I ever ate Chinese food I loved it．I noticed the fresh taste of the meat and vegetables．When I learned more about the food，I beganto understand why it has this special feature． Many years ago，China had an energycrisis(危机)because it lost much of its wood due to over populationand poor management of its forests．This loss was verybad for the country，of course，butit turned out to be very good for the food．Wood becamevery expensive and hard to get，so the Chinese had toeither find a substitute(替代物)for their valuable wood，or learn how to use it better．There weren’tany substitutes so people found ways to—economize． In order to economize in cookin9，they had touse very little wood．So they started cutting their meatand vegetables into small pieces before they put them in the hot oil．That way，the food cooked faster and theysaved their fuel。The food prepared in this way kept its fresh flavor(味道)一and it’s thisflavor that attracts people from other countries to the art of Chinese cooking． It can beinferred from the text that before the energy crisis Chinese food（） A: was cooked in rather large pieces B: was cooked in water but not oil C: didn’t taste good D: didn’t look fresh