民用航空器是指（）的航空器。
A.执行军事任务
B.执行海关任务
C.执行警察任务
D.除上述三项外的
参考答案：D
With the improvement of people's living conditions, most mothers _______ in hospitals. [ ]
A. have delivered their babies
B. have born their babies
C. have their babies born
D. have their babies delivered
报纸引起读者阅读的稳定兴趣的特性被称为（）。
A、可读性
B、可信度
C、定读性
D、穿透力
