具体餐饮产品生命周期阶段的特点体现在________、成长期、成熟期、衰退期4个阶段。
参考答案：成熟期无限延长型
Though I have often heard this song ______, I have never heard you ______ it. [ ]
A. being sung; sang
B. sang; singing
C. sung; sing
D. to be sung; to sing
面对张六拒收的情况，法院应如何处理
