题目

—Have the workers got our roof repaired? —I don't know. But it____ when I called them yesterday. A . was repairing B . was repaired C . had repaired D . was being repaired 答案：D如图是初中化学中常见物质间的转化关系，其中甲、乙、丙为单质；A、B、C、D、E为化合物，且A与B的组成元素相同，D与E的组成元素也相同．已知C、丙均为黑色粉末，C和E在高温条件下反应可生成丙和D，其余反应条件、部分反应物和生成物均已略去．试推断：（1）写出有关物质的化学式：A 、B 、乙 、E ．（2）写出下列化学方程式：甲→C： ；C+E→丙+D： ．