单选：热水供暖系统（）不热的主要原因是管道堵塞、阀门失灵、气阻等。A．吸气管B．散热器C．出水口D．水平干管

采暖管道的防腐刷油（）按材质、除锈方式、除锈标准、涂料种类计。A．延长米计算B．保护层计算C．保温层计算D．工程量计算

[完型填空] Last night, a fire broke out in Ann's house in Manchester. ...

先天性甲状腺功能减退分类正确的是（）A．遗传性、非遗传性B．散发性、地方性C．碘缺乏性、非碘缺乏性D．原发性、继发性、散发性E．碘缺乏性、非碘缺乏性、混合性

[阅读理解] Mark was walking home from school one day when he noticed a boy a...

[阅读理解]Shyness is the cause of much unhappiness for a great many people. Shy...