test B 21

21.   A peculiar feature of the embryonic mammalian circulatory system is that in the area of the heart the cells adhere to one another, beating in unison and adopting specialized orientations exclusive of one another.

(A) beating in unison and adopting

(B) they beat in unison while adopting

(C) beat in unison, and adopt

(D) beating in unison yet adopting（D）

(E) even though they beat in unison and adopt

我认为是选C。adhere to ,beat ,and adop 是平行的。

请指教

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谢谢配合。

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http://forum.chasedream.com/dispbbs.asp?boardID=23&ID=81499&page=1