电网终端的保护,过电流保护动作时限并不长,可以作为主保护兼后备保护。( )
查看答案
How does Little Brad comfort his mother？
A. He says that they can overcome the difficulties.
B. He says that they can find a different way.
What does Little Brad want to say to his Dad？
A. He makes those weird actions willfully.
B. He make those weird actions unintentionally.
混凝土中的水泥砂浆，在混凝土硬化前后起( )作用
A. 胶结
B. 润滑和胶结
C. 填充
D. 润滑和填充
缓凝剂、早强剂和速凝剂属于()。
A. 改善混凝十其他性能的外加剂
B. 改善洮凝土耐久性的外加剂
C. 改善混凝土拌和物流动性能的外加剂
D. 调节混凝土凝结时间和硬化性能的外加剂
微信支付 
支付宝支付