题目

阅读理解The boy sat on his chair,with his hands above the keyboard. He thought about what to write.He recalled that the competitiondeadline was merely a week away. But he still had not even started on his piece.He looked at the brochure again. WRITING COMPETITION! the title read.His mum had encouraged him to enter the writing competition, and now he was takingit on as his personal task for the holidays.As the boy reflected onhis previous writing efforts, he realised how hopeless his task of winning was.Every story he ever wrote was based on other stories. He had little imagination,and unfox是40℃的硝酸钾溶液，进行如下操作后，判断错误的是( )A. X一定是不饱和溶液B. Y可能是饱和溶液C. Y的溶质质量分数一定比Z大D. X和Z的溶质质量分数一定不相等