【单选题】What s the author s attitude toward McDonald s present situation?
【简答题】一个水池有两个排水管甲和乙,一个进水管丙。若同时开放甲、丙两管,20小时可将满池水排空;若同时开放乙、丙两水管,30小时可将满池水排空;若单独开丙管,60小时可将空池注满。若同时打开甲、乙、丙三水管,要排空水池中的满池水,需几小时?
【单选题】一个游泳池,甲乙两个进水管,丙是出水管,甲进水管放满水需要8个小时,甲乙两个进水管同时开放放满水需要6个小时,丙用2个小时就可以把半池水排尽。当游泳池有半池水时,假设同时开放乙丙两管,问需经过多长时间才能把游泳池的水排空?( )
【单选题】一个水池有甲乙两个排水管,一个进水管丙。甲丙同时开,20小时可以把水池排空;同 时开乙丙两管,30小时排空;单独开丙管,需要60小时注满。若三管齐开,需要( )排空水池。
【简答题】一个水池有两个排水管甲和乙,一个进水管丙。若同时开放甲、丙两管,20小时可将满池水排空;若同时开放乙、丙两水管,30小时可将满池水排空;若单独开丙管,60小时可将空池注满。若同时打开甲、乙、丙三水管,要排空水池中的满池水,需多少小时?( )
【单选题】一个水池有甲乙两个排水管,一个进水管丙。若同时开放甲丙两管, 20 小时可将满池水排空;若同时开放乙丙两水管, 30 小时可将满池水排空,若单独开丙管, 60 小时可将空池注满。若同时打开甲乙丙三水管,要排空满水池,,需几个小时?
【简答题】一个蓄水池有甲、乙两个进水管和一个丙排水管,单独开甲管6小时可注满水池;单独开乙管8小时可注满水池,单独开丙管9小时可将满池水排空,若先将甲、乙管同时开放2小时,然后打开丙管,问打开丙管后几小时可注满水池?
【单选题】保险中的风险是指损失发生的不确定性,即()。
D.
损失发生时间、地点及其后果在主观认识上的难以确定和预料
【单选题】The author implies that scientists develop a healthy skepticism because they are aware that ______.
A.
mathematicians are better able to solve problems than scientists
B.
changes in axiomatic propositions will inevitably undermine scientific arguments
C.
well-defined situations are necessary for the design of reliable experiments
D.
some factors in most situations must remain unknown
【单选题】We (are obliged) to grow up in skepticism, requiring proofs for every assertion about nature, (but) there is no way out (except) to move ahead and plug away, hoping for comprehension in the future (bu...