Our Earth will be ________ if we go on cutting down millions of trees every year.

A．in great danger

B．danger

C．dangerously

D．out of danger

骶尾部畸胎瘤症状与体征与哪些因素有密切关系？（）

A.年龄

B.肿瘤大小

C.肿瘤类型

D.有无恶变

E.是否继发感染