问题 单项选择题

逆转录病毒载体系统的缺点是:

A.感染细胞量大
B.稳定性较好
C.病毒滴度较高
D.只能整合至分裂相的细胞
E.转染谱广

答案

参考答案:D

解析:[解题思路] 逆转录病毒载体系统的特点。逆转录病毒载体系统的特点包括转染谱广、感染细胞量大、稳定性较好、病毒滴度较高,D选项与E选项矛盾,故E选项是正确答案。

完形填空
Man began to make use of fire long long ago. Fire is useful in many ways, but sometimes it is dangerous. If you are not (1)        with it, it can burn things or (2)       hurt you. A big fire can (3)        forests and tall buildings. Sometimes a piece of (4)        paper can cause a big fire. So please remember (5) ______      in the dry places like woods and forests (6)        throw a cigarette end on the grass and it’s also important for you to put the candles in the 7)       place. When you use candles at home ,you should (8)        your long hair away from the fire.
But if there is a (9)        in our building, what should we do with it? Pour some water (10)       your clothes. What’s more, put a (11)        towel (毛巾) over your mouth and your nose to keep the (12)______                out. You’d better run away from the fire as (13)        as you can. But you mustn’t rush! Or you may fall over and hurt yourself or others. Of course you should also call 119. On the phone you should clearly tell the firemen (14)      the fire is to help them get there without difficulty. By the way, Do not (15)        out of the window. Jumping may be more dangerous than the fire.
Keep ourselves away from fire and safety is above all!
小题1:
A.carefulB.happyC.pleasedD.strict
小题2:A. even          B still            C. also              D. always
小题3:
A.washB.blowC.burnD.hit
小题4:
A.blackB.whiteC.thickD.thin
小题5:
A.not to swimB.not to smokeC.don’t swimD.don’t smoke
小题6:
A.andB.orC.and notD.or not
小题7:
A.quietB.noisyC.wrongD.right
小题8:
A.makeB.putC.keepD.take
小题9:
A.forestB.piece of paperC.fireD.an area of grassland
小题10:
A.aboveB.belowC.overD.under
小题11:
A.dryB.bigC.smallD.wet
小题12:
A.airB.smokeC.waterD.fire
小题13:
A.slowlyB.quicklyC.happilyD.early
小题14:
A.whereB.whenC.whatD.how
小题15:
A.runB.rushC.getD.jump
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