将中国古代政治制度“①三省六部制②行省制③郡县制”按产生先后次序排列，正确的是[ ]
A．①②③
B．③①②
C．③②①
D．②①③
答案：B
群落之间、群落与环境之间相互关系的可见标志是( )
A．群落外貌 B．群落水平结构C．群落垂直结构 D．生态位
One of my close friends made great progress in her studies so her teachers ___ her, and I _____ her.
A．were happy with; was happy with
B．were happy for; was happy for
C．were happy with; was happy for
D．were happy for; was happy with
