seems to be one of the main reasons for many people        in today’s world.

A．Having an adventure; to travel

B．To have an adventure; traveling

C．Have an adventure; to travel

D．To give an adventure; traveling

免疫自稳功能异常可发生

A．病毒持续感染

B．肿瘤

C．超敏反应

D．自身免疫病

E．免疫缺陷病