植物体的长高、增粗主要是由于顶端分生组织细胞分裂、生长和分化的结果。( )
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周皮是由初生分生组织细胞分裂、分化产生的，由木栓层、木栓形成层、栓内层三部分构成。( )
Which of the following is most unlikely for the authoi to do？
A. To talk to the students who have mental problems．
B. To help students develop a feeling of self-respect．
C. To keep a student from playing alone．
D. To announce a student’s scores in public．
Tigers would__________ if men were allowed to shoot as many as they wished．
A. die down
B. die out
C. die away
D. die off
Her suggestion that everybody__________ was not appreclated.
A. sing a song
B. sang a song
C. sung a song
D. singing a song
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