某校附近有一家小店，店主经常向未成年学生出售散装卷烟 ，并容留他们在店内吸烟，有些学生因此经常光顾这家小店。该店主的行为没有履行对未成年人(        )的义务。                     

    It is Sunday today but my three good friends are not at home. Tina is at the mall. Is she shopping? No, she isn't. She is eating lunch with one of her friends. Mike is still at school. Is he doing his homework? No, he isn’t. He's playing basketball with other boys. What about Lisa? Where is she? She is at the library. She is reading a book. Is it an interesting book? Yes, it is. Lisa likes this book very much.

如图是某旅游城市近几年来游客人数统计图．

明朝中后期资本主义萌芽的标志是（    ）