问题 单项选择题

假设消毒时的细菌灭活速率与细菌个数为一级反应关系,消毒过程中,细菌数量从n0。减少到n0/2需要10s,则从n0/2减少到n0/4的时间是()。

A.5s

B.10s

C.20s

D.40s

答案

参考答案:B

解析:

据题意,反应器为PF型或CMB型。其模型查《考试教材》第1册表5—4,均为。式中k是反应常数,所以t仅与C0/Ci有关。由于,所以它们消耗的时间也相同。

完形填空
Last spring, I was fortunate to be chosen to participate in an exchange study program. In my application letter, I was careful to   21  how much I wanted to see France; evidently, my excitement really came through in my words. Once I   22   that I was going, all I could think about was the fun of foreign travel and making all sorts of new and   23  friends. While traveling was inspiring and meeting people was   24  , nothing about my term in France was what I   25 .       
The moment I arrived in Paris, I was   26  by a nice French couple who would become my host parents. My entire experience was joyous and exciting  27  I received some shocking news from my program coordinator(协调人): there had been a death in my host parents’ extended family. They had to travel outside France for several weeks. That afternoon, I had to   28  out of one family’s house into another. The exchange coordinator told me I’d have a   29  this time and asked whether I could share a bedroom with an English speaker. To avoid the temptation(诱惑) to   30 my native language, I asked not to be   31  with an English-speaking roommate. When I got to my new room, I   32  myself to my new roommate Paolo, a Brazilian(巴西人) the same age as I, whom I was surprised to find playing one of my favorite CDS! In just a few hours, we knew we’d be good friends for the rest of the   33  .      
I left France with many   34  , so when people asked me what my favorite part of the trip was, they are always   35  to hear me talk about my Brazilian friend Paolo and scores of weekdays in class, weeknights on the town, and weekends   36  France we enjoyed together. I love how people   37  seem so different, but end up being so   38  . The most valuable lesson I gained from studying in France wasn’t just to respect the friend people   39  to respect all people, for your next best friend could be just a continent away. I would recommend an exchange program to anyone who wants to experience foreign cultures and gain meaningful  40  .   
小题1:
A.discussB.expressC.announceD.argue
小题2:
A.approvedB.knewC.warnedD.denied
小题3:
A.stubbornB.anxiousC.universalD.interesting
小题4:
A.boringB.upsettingC.excitingD.promising
小题5:
A.expectedB.likedC.doubtedD.feared
小题6:
A.sponsoredB.witnessedC.greetedD.supported
小题7:
A.untilB.when C.sinceD.while
小题8:
A.moveB.travelC.walkD.rush
小题9:
A.housekeeperB.leaderC.roommateD.colleague
小题10:
A.learnB.appreciateC.speakD.master
小题11:
A.combinedB.fittedC.involvedD.placed
小题12:
A.addedB.introducedC.devotedD.adapted
小题13:
A.termB.weekC.monthD.vocation
小题14:
A.presentsB.suitcaseC.storiesD.dreams
小题15:
A.surprisedB.disturbedC.embarrassedD.concerned
小题16:
A.analyzingB.exploringC.describingD.investigating
小题17:
A.needB.shallC.mustD.can
小题18:
A.generousB.independent C.similarD.distant
小题19:
A.andB.butC.orD.so
小题20:
A.instructionsB.friendshipsC.factsD.data
单项选择题