参与一碳单位传递的维生素有（）。 A.维生素C B.维生素B6 C.叶酸 D.维生素

飧泄是指（）

A.大便稀溏

B.泄泻无度

C.大便完谷不化

D.下利脓血

E.濡泻

She was educated at Beijing University, _____ she went on to have her advanced study abroad. [ ]

A. after which

B. from which

C. from that

D. after that

试说明栅格数据结构的概念，以及它的特点和获取方法？

锚喷工应做到哪五个不喷？

普通话的声母一共二十一个，它们都是辅音。