关于子宫内膜，下列哪项错误（）

A.月经来潮子宫内膜自基底层剥脱

B.子宫内膜分功能层与基底层

C.子宫内膜基底层无周期性变化

D.子宫内膜为单层柱状上皮

E.子宫内膜有腺体、间质和血管

The little boy finished the work       and didn’t ask anyone for help. [ ]

A.by the way

B.on his own

C.of his own

D.all the time