吊顶工程常见的质量问题有（）
A．吊顶龙骨起拱不均匀
B．面层变形
C．板面开裂
D．龙骨间距不含要求
参考答案：A, B, C
What a pity! I hear they _______ the tickets for the concert.[ ]
A. have sold out
B. are selling out
C. sold out
D. had sold out
个体产生新奇独特的、有社会价值的产品能力或特性称之为______。
