问题 单项选择题

下列有关遗传物质的描述,错误的是()

A.细胞生物的遗传物质都是DNA

B.任何生物的遗传物质只有一种

C.肺炎双球菌的遗传物质是DNA或RNA

D.不含DNA的生物,RNA是其遗传物质

答案

参考答案:C

解析:细胞生物含有DNA和RNA,遗传物质是DNA;病毒只含一种核酸(DNA或RNA),遗传物质是DNA或RNA,所以任何生物的遗传物质只有一种;肺炎双球菌的遗传物质是DNA;不含DNA的生物,RNA是其遗传物质,如少数病毒。故选C

完形填空
When I entered Berkeley,I hoped to earn a scholarship.Having been a Straight­A student,I believed I could ____tough subjects and really learn something.One such course was World Literature given by Professor Jayne.I was extremely interested in the ideas he ____in class.
When I took the first exam,I was ____ to find a 77,C­plus,on my test paper,____ English was my best subject.I went to Professor Jayne, who listened to my arguments but remained  ____.
I decided to try harder.Although I didn't know what that ____because school had always been easy for me.I read the books more carefully,but got another 77.Again,I ____with Professor Jayne.Again,he listened patiently but wouldn't change his ___.
One more test before the final exam.One more ____ to improve my grade.So I redoubled my efforts and,for the first time, ____the meaning of the word “thorough”.But my ___ did no good and everything ___ as before
The 1ast hurdle(障碍)was the final.No matter what ____ I got,it wouldn't cancel three C­pluses.I might as well kiss the ____ goodbye.
I stopped working hard.I felt I knew the course material as well as I ever would.The night before the final,I even ____ myself to a movie.The next day I decided for once I'd have ____ with a test.
A week later,I was surprised to find I got an A.I hurried into Professor Jayne's office.He  ______to be expecting me.“If I gave you the As you ____,you wouldn't continue to work as hard.”
I stared at him,____ that his analysis and strategy(策略)were correct.I had worked my head  ____,as I had never done before.
I was speechless when my course grade arrived:A­plus.It was the only A­plus given.The next year I received my scholarship.I've always remembered Professor Jayne's lesson:you alone must set your own standard of excellence.
小题1:
A.takeB.discussC.coverD.get
小题2:
A.soughtB.presentedC.exchangedD.obtained
小题3:
A.shockedB.worriedC.scaredD.anxious
小题4:
A.butB.soC.forD.or
小题5:
A.unchangedB.unpleasantC.unfriendlyD.unmoved
小题6:
A.reflectedB.meantC.improvedD.affected
小题7:
A.quarreledB.reasonedC.bargainedD.chatted
小题8:
A.attitudeB.mindC.planD.view
小题9:
A.choiceB.stepC.chanceD.measure
小题10:
A.memorizedB.consideredC.acceptedD.learned
小题11:
A.ambitionB.confidenceC.effortD.method
小题12:
A.stayedB.wentC.workedD.changed
小题13:
A.gradeB.answerC.lessonD.comment
小题14:
A.scholarshipB.courseC.degreeD.subject
小题15:
A.helpedB.favoredC.treatedD.relaxed
小题16:
A.funB.luckC.problemsD.tricks
小题17:
A.happenedB.provedC.pretendedD.seemed
小题18:
A.valuedB.imaginedC.expectedD.welcomed
小题19:
A.rememberingB.guessingC.supposingD.realizing
小题20:
A.outB.overC.onD.off
单项选择题