As we all know,tigers and cats________the same family of beasts.[ ]

A. belonged to  

B. are belonged to

C. belong to  

D. are belonging to

关于子宫内膜癌彩色多普勒经腹超声表现，下列哪一项是错误的（）。

A.肿瘤内部可见较丰富血流

B.肿瘤血管RI小于0.45

C.肿瘤血管RI大于0.8

D.肿瘤周边可见丰富血流

E.肿瘤血管RI对鉴别诊断有帮助