9．家兔营草食生活，身体的下列结构与此相适应的是

①牙齿分化为门齿和臼齿                       ②心脏有四个腔

③血液循环有两条途径                         ④有发达的盲肠

A．①③                      B．①④                      C．②③                      D．②④