We should do what we can to save those_________ species, for example, the tiger, an animal which was considered_______ to humans.

A．dangerous; endangered

B．dangerous; in danger

C．endangered; in danger

D．endangered; dangerous

以下哪项不是骨巨细胞瘤的CT征象（）。

A.肿瘤呈膨胀性表现

B.骨质有中断现象

C.肿瘤内可见钙化

D.肿瘤中心可见坏死、液化

E.肿瘤边缘可见骨嵴