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Passage Two Questions 26 to 30 are based on the following passage. In our day of the automobile and paved highway few people ever encounter quicksand(流沙). Yet quicksand is still common in many pans of the country. It may be more dangerous for being less familiar. Quicksand is usually found along the shores and in the beds of rivers. It is simply sand saturated(使饱和)with water from beneath，as from a spring. The water flowing into the sand separates the grains. The suspended grains give rather easily and a heavy object placed on the surface is likely to sink. How fast it sinks depends on its weight and surface area. How does one detect quicksandIt cannot be done by the eye alone，since sand which looks firm may suddenly collapse and trap anyone who ventures out on it. The only way to be sure is to test A. that today few people ever encounter quicksand B. that quicksand is still common in many parts of the country C. that quicksand cannot be detected by the eye alone D. expressed by none of the above [单选题]BY. 2型逆变器设有自保护装置，当逆变器工作的温度或电流超过规定值时，（ ）导通，逆变器停止工作。
A.可控硅 B.三极管 C.二极管 D.继电器 [单项选择]在“生民之祸亟矣”中，“亟”之义为（）
A. 急 B. 频繁 C. 极 D. 多次 [多选题]爆破采煤工作面()工序应避免相互干扰,最好将两道工序安排在不同班中作业。(1.0分)
A.移送输送机 B.回柱 C.装煤 D.放炮 [单选题]妊娠期血容量增加达到高峰的时期是在妊娠
A.28～30周 B.30～32周 C.32～34周 D.34～36周 E.36～38周 [多选题]超声探伤装置的灵敏度（）。
A.脉冲发生器探头 B.接收器的组合性能 C.随分辨率的提高而提高 D.与换能器的机械阻尼无关 [判断题]机械伤害造成的受伤部位可以遍及我们全身各个部位，若发生机械伤害事故后，现场人员应先看神志、呼吸，接着摸脉搏、听心跳，再查瞳孔。
A.正确 B.错误 [单选题]挖到电缆保护板后，应由（ ）在场指导，方可继续进行。
A.工区领导 B.工作负责人 C.有经验的人员 D.运维人员 [单选题]两个车钩连挂后,其两个车钩的中心线相差不得超过( )。
A.74mm B.75mm C.76mm [单项选择]新斯的明治疗重症肌无力的主要作用机制是
A. 直接激动N1受体 B. 抑制递质的贮存 C. 抑制ACh的生物合成 D. 抑制ACh的酶解 E. 以上均不是 我来回答: 提交
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