下列物质性质的变化规律,与键能无关的是(　　)

①HF、HCl、HBr、HI的热稳定性依次减弱

②NH₃易液化

③F₂、Cl₂、Br₂、I₂的熔、沸点逐渐升高

④H₂S的熔、沸点小于H₂O的熔、沸点

⑤NaF、NaCl、NaBr、NaI的熔点依次降低

已知复数  z₁=3-bi,z₂=1-2i，若 $\frac{z_1}{z_2}$是实数，则实数 b 的值为（  ）

阅读下面的材料，回答问题．

现代社会关于“健康”的概念已超越了传统的医学观点，不仅包括躯体、生理健康，还包括精神、心理 健康．当今社会竞争激烈，造成人们心理压力重，在校中小学生在这样的社会大环境下生存，面临升学压力，心理脆弱，心理压抑得不到一定的宣泄；另外，我国独 生子女以自我为中心的问题也显得越来越严重；更有甚者，由于家庭的残缺，如父母离异、丧父或丧母的单亲家庭，留守儿童，隔代抚养孩子等现象，都使孩子缺乏 良好的生活和教育环境．学校里各种不良现象屡禁不止，各种失控越轨行为时有发生，原因固然是多方面的，但与学生的心理健康水平不高，心理素质差有极大的关 系．我们不但要重视学生生理健康，更重视心理健康，学生学会自我心理调节的方法更为重要．

阅读下面材料，在空白处填入适当的内容(1个单词或括号内的单词的正确形式)。
    Earthquakes are quite common. In fact, thousands of earthquakes happen each day. Most of them are ____ weak to feel, though. During a big earthquake, there is often a big noise first. Then the earth shakes ____(terrible) and many houses fall down.
     As one of the most deadly natural  ____（disaster) in the world, earthquakes often result in many people being injured or killed. In 2008, a severe earthquake hit China's Sichuan Province, which____(kill) more than 80,000 people there.  
    Besides, the great damage and deaths caused by the earthquake____(it), other accidents such as fires often follow.____ (much) buildings may be damaged and more deaths may be caused.
    For centuries, man have been making studies of earthquakes. About 2,000 years ago, for example, a Chinese scientist named Zhang Heng invented a machine, which could find out from which direction the earthquake waves came. With the rapid ____(develop) of modern science and technology, we now know a lot more about earthquakes. However, scientists still have
difficulty ____ (predict) exactly when and where ____earthquake will happen, and can't stop it ____happening.

公元7世纪时，日本孝德天皇颁布改新诏书，进行改革，史称“大化改新”。这次改革仿效的是（    ）