问题 选择题

馒头是利用酵母菌发酵制作出来的,但馒头吃起来却没有酒味这是因为(  )

A.酵母菌在发酵时根本没有产生酒精

B.酒精在蒸馒头时挥发掉了

C.馒头中的酒精转变成了其他物质

D.发面中的酒精含量很少

答案

做馒头的时候用到了酵母,但是酵母菌是一种兼性厌氧型真菌,所以它既能进行有氧呼吸,也能进行无氧呼吸.在有氧的环境下,酵母菌会进行有氧呼吸产生二氧化碳和水.只有在无氧的环境下,它才会进行无氧呼吸,即酒精发酵,产生酒精.而一般做馒头是在有氧的环境下做的,即便在烤面包或蒸馒头的过程中有无氧呼吸产生酒精,而酒精易挥发.可见B符合题意.

故选:B

阅读理解

阅读理解

     Both my parents came from towns in Mexico.Then I was born in El Paso,  Texas,  and when I was

four,  my family moved to a housing project in East Los Angeles.

     Even though we struggled to make ends meet,  my parents stressed to me and my four brothers and

sisters how fortunate we were to live in a great country with limitless opportunities.They influenced us

with the concepts of family,  faith and nationalism.

     I got my first real job when I was ten.My dad injured his back working in a cardboardbox factory

and was retrained as a hairstylist.He rented space in a little shopping mall and gave his shop the fancy

name of Mr Ben's Coiffure.

     The owner of the shopping center gave Dad a discount on his rent for cleaning the parking lot three

nights a week,  which meant getting up at 3 a. m..To pick up rubbish,  Dad used a little machine that

looked like a lawn mower.Mom and I emptied garbage cans and picked up litter by hand.It took two

to three hours to clean the lot.I'd sleep in the car on the way home.

     I did this for two years,  but the lessons I learned have lasted a lifetime.I acquired discipline and a

strong work ethic (道德),  and learned at an early age the importance of balancing life's competing

interests-in my case,  school,  homework and a job.This really helped during my senior year of a high

school,  when I worked 40 hours a week flipping burgers at a fastfood joint while taking a full load of

college preparation courses.

     The hard work paid off.I attended the US Military Academy and went on to receive graduate

degrees in law and business from Harvard.Later,  I joined a big Los Angeles law firm and was elected

to the California State Assembly (州议会). In these jobs and in everything else I've done,  I have never

forgotten those nights in the parking lot.The experience taught me that there is dignity in all work and that

if people are working to provide for themselves and their families that is something we should honor.

1. Before my father got injured,  we________.

A. didn't like living in the USA

B. lived a poor but happy life

C. were lucky to move to the USA

D. had many ways to make money

2. When he recovered,  to make a living my father________.

A. ran a small shopping mall

B. did a parttime job

C. worked as a barber

D. became a street cleaner

3. Working in the parking lot for two years had taught me________.

A. how to obey school discipline

B. how to do two things well at a time

C. that discipline and work were of equal value

D. that I must do as many things as possible at a time

4. The author tells us in the last paragraph that we should be proud of those who________.

A. have done all kinds of jobs

B. are cleaning the parking lot

C. have achieved a lot in their lives

D. are bearing their responsibilities

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