井下技术状况是指封隔器工作状况、（）等。 ["A.蜡堵、砂堵、窜槽、套管变形","B.窜槽、套管变形","C.蜡堵、砂堵、套管变形","D.蜡堵、砂堵、窜槽"]
进入成长期的企业战略重点是（） ["产品开发战略","市场开发战略","综合的竞争战略","退出战略"]
如果网络入侵者是在防火墙内部，则防火墙是无能为力的。
The static suction lift of a pump is the difference in elevation between the （）. ["centerline of the pump and the level of the liquid in the suction well when the source of liquid is below the pump","centerline of the pump and the suction liquid level when the source of liquid is above the pump","centerline of the pump and the level of the discharge liquid","liquid levels of the suction and discharge"]
防火墙可以阻止感染了病毒的软件或文件的传输。
试述光纤材料色散的定义及其引起的原因。
