热量计所用的氧弹是由（）制成的气密容器。 ["A.18\/3铬镍钢 ","B.18\/8铬锌钢 ","C.18\/8铬镍钢 ","D.18\/3铬锌钢"]
船舶强度大，马力大，稳性和浮性较好，但船体较小的船舶称为（） ["海洋开发船；","航标船；","拖船；","破冰船。"]
大脑皮层上的枕叶是（） ["听觉中枢","视觉中枢","言语中枢","嗅觉中枢"]
简述岩石爆破破坏原理和假说。
冶炼75硅铁，要求硅石中Al2O3应小于（） ["0.01%","1.0%","0.02%","0.20%"]
何为有效灌溉的耕地面积？
