单项选择题

红外光谱中三种伸缩振动vC=O、vC—H、vC—C的频率大小是______。
   A.VC=O>VC—H>VC—C;    B.  VC—C>VC—H>VC=O
   C.VC—H>VC—C>VC—O;    D.VC—H>VC—O>VC—C

A.VC=O>VC—H>VC—C
B.VC—H>VC—C>VC—O
C.VC—H>VC—O>VC—C