－How about going on a school trip this weekend?

－That sounds _____. I like going outside.

A．boring

B．easy

C．interesting

D．difficult

确定给氧浓度的首要指标为：【 】

A．紫绀的轻重

B．病情和血气检查

C．呼吸困难的程度

D．神志状态

E．肺功能检查结果