Because this area has a high rate of crime and unemployment, there are only people moving out.

A．incentive

B．incident

C．incidence

D．initiative

形成层环呈多角形，内外侧偶有1至数个异型维管束的药材为

A．大黄
B．何首乌
C．牛膝
D．商陆
E．川乌