提示诊断肺气肿的最有价值的肺功能检测指标是（）。

A.肺活量

B.肺总量

C.残气量

D.残气量／肺总量%

E.通气／血流

  I’d love to go to the English evening. But I’m a little ________, because I will be asked to sing an English song in front of the whole school.

A．tired

B．sad

C．nervous

D．pleased