It's hard to keep the children ________ when they can't go outside and play.[ ]

A. amused

B. being amused

C. from being amused

D. amusing

二级资质及二级资质以下的房地产开发企业可以承担建筑面积（）万平方米以下的开发建设项目，承担业务的具体范围由省、自治区、直辖市人民政府建设行政主管部门确定。

A.15

B.20

C.25

D.30