立位片上，腹部游离气体的典型影像为（）。
A.球形
B.不规则形
C.新月形
D.半球形，有"气液面"
E.与胸腔间距大于15mm
参考答案：C
产后抑郁
After two hours the children got to the hill, tired ______ happy. [ ]
A. and
B. but
C. although
D. however
