第3题: [单项选择]The most important consideration for manned space flight is that the rocket be ______. A. inexpensive to construct B. capable of lifting heavy spacecraft into orbit C. easily controlled D. inexpensive to operate 参考答案:C 答案解析:文中提到manned space flight needs the fine adjustments only be provided by liquid fuels,而前文讲了液体燃料火箭rocke
第4题: [单项选择]综合安全技术 建筑灭火器的适用范围,扑救A、B、C类和带电火灾应选用( )。 A. 水、泡沫、磷酸铵盐干粉、卤代烷型灭火器 B. 干粉、泡沫、卤代烷、二氧化碳型灭火器 C. 磷酸铵盐干粉、卤代烷型灭火器 D. 碳酸氢钠干粉、卤代烷、二氧化碳灭火器 参考答案:C
第6题: [单项选择]Overheating of a hydraulic system may be a result of (). A. changing pump discharge pressure in response to normal load variations B. a high oil level C. incorrect fluid viscosity D. continued slow re-circulation of the oil 参考答案:C
第7题: [单项选择]超声引起细胞和组织发生变化的机制是() A. 振动和辐射 B. 吸收和反射 C. 直接和间接 D. 热和空化效应 E. 以上均不是 参考答案:D