如图所示，在水平地面上，一条形磁铁附近的一铁块处于静止状态。下列说法中正确的是（   ）

在数轴上表示数：﹣2，+1.5，﹣ $\frac{1}{2}$ ，0， $\frac{5}{2}$ ，﹣3，按从小到大的顺序用“＜”连接起来．

请根据氧化还原反应Fe+2H⁺═Fe²⁺+H₂↑设计成原电池：

阅读判断。
    Jenny, Danny, Kim and Steven are good friends. Jenny and Kim are reading books in the library. Where are Danny and Steven? Look! They are playing a game on the playground. Who is in the classroom? It's Mr. Wood.

熔丝材料的特点是（   ）