[填空题]A man steps on what seems like solid ground but discovers with horror that the ground is giving way beneath his feet. The man struggles (36) , but he is mercilessly (37) He cannot escape. Slowly he sinks deeper and deeper until at last he is gone, (38) in the treacherous earth. The solid ground was solid only in (39) It was actually quicksand, which is a deep (40) of fine sand mixed with water.
How is quicksand formed Water pushes up from below the surface and is held by the sand. The (41) of sand are forced apart by the water. They cannot hold any weight. The subsurface water may have come from a spring, a river, or a stream. Sometimes pools of water near beaches become filled with sand. When the soil under these pools does not allow for good drainage, the sand can become (42) of quicksand.
Is it true that a man who steps into quicksand is (43) to die No, four men have fought the

最新试题

• ●    知觉的基本特性有( )。
• ●    [单选题]在车站一端宜设( )，装设隔离开关，纳入远动控制并视频监控。
• ●    [多选题]下列说法中符合柜员尾箱管理规定的有（）
• ●    孔的基本偏差从A到H、轴的基本偏差从A到h分别为（）偏差。
• ●    [单选题]侧向接发停车货物列车并位于正线的单开道岔,在中间站不得小于( )号,在其他车站不得小于
• ●    [单选题]大修后的变压器在投运时一般需冲击（）。