下列对艾滋病和血吸虫病的认识，正确的是（    ）

①二者都是严重危害人类健康的传染病  ②二者都是目前不可治愈的严重疾病  ③未成年人不可能感染上这两种疾病  ④这两种疾病都是可以预防的

    Breakfast is very important. It is one of the most important1of the day. To keep healthy, everyone should2a good breakfast.3the right food is necessary for good health. We may have eggs, bread, milk and so on,4breakfast. Many students go to school without breakfast5they get up late or their parents don't cook for them. It's6for their health.7breakfast children may not grow fast and may not study and play very well at school. They may8. And when they're ill, they will9a long time in recovering (恢复). I think everyone should have some good10habits. It is necessary.

元素X的单质及X与Y形成的化合物能按如图所示的关系发生转化(其中m≠n，且均为正整数)。下列说法正确的是（      ）