接收并阅读由ncre@mail.neea.edu发来的E—mail。并将附件另存在考生文件夹中。
参考答案：
解析：略
He__________unwisely, but he was at least trying to do something helpful．
A．may have acted
B．must have acted
C．should act
D．would act
直流电动机发生环火的原因有：设计原因，换向器维护不良，换向器恶化和电气控制系统故障。（）
