被子植物维管束中的导管发育成熟时，端壁部分被溶掉而形成穿孔，穿孔可分为( )和( )两种。
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双子叶有胚乳种子由( )、( )和( )三部分构成。
We can conclude fromthis passage that ballet
A. is a dying art
B. will continue to change
C. is currently performed only in Russia
D. is often performed by dancers with little training
判断下列植物各属于哪个科？
小麦( ) 灰绿藜( ) 一串红( ) 草莓( )
板栗( ) 乌蔹莓( ) 蜀葵( ) 夏至草( )
郁金香( )芹菜( )
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