定张减机区主要缺陷有哪些？
参考答案：
结疤、麻面、青线、轧折、断裂、钢管长度超差、直径超差、壁厚超差、壁厚不均。
—Did you know more about the mine accident?
—Oh, sorry, I had no idea. I ____the Rescue Center now.
A．will be phoning
B．am to phone
C．will phone
D．phone
高度近视周边视网膜变性伴有玻璃体牵拉时可导致( )
A．裂孔性视网膜脱离B．渗出性视网膜脱离C．牵拉性视网膜脱离D．多灶性视网膜脱离E．大泡性视网膜脱离
