植物体内某些成熟细胞，在一定条件下，会失去成熟细胞的特性而恢复到具有分裂能力的细胞状态，这种现象称为脱
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Few airlines want to impose a total ban on their passengers using electronic devices because．
A. they don’t believe there is such a danger as radio interference
B. the harmful effect。of electromagnetic interference is not yet to be proved
C. most passengers refuse to take a plane which bans the use of radio and cassette players
D. they have other effective safety measures to fall back on
Because of the way she had been behaving，Martin felt__________in leaving her．
A. hopeful
B. sensitive
C. justified
D. valid
People in many developing countries are__________into overcrowded cities in great numbers．
A. filling
B. hurrying
C. pouring
D. breaking
According to the passage our failure to give proper response to the speaker is probably because
A. we misunderstand what he says
B. he speaks in a distorted wav
C. we don’t like the speaker
D. he spear in a different language
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