The crankshafts on the large modern 2-stroke crosshead engines are （）big （）makes as a single unit and so are constructed by joining together individual forgings. ["enough；to","too；to","such；so","so；that"]
常闭按钮的电工符号是
（）的设计文件，应当经国务院特种设备安全监督管理部门核准的检验检测机构鉴定，方可用于制造。 ["锅炉","大型游乐设施","起重机械","客运索道"]
国家鼓励特种设备节能技术的（），促进特种设备节能技术创新和应用。 ["A.研究","B.开发","C.示范","D.推广"]
刘白羽抒情散文代表作是（）。 ["《朝鲜在战火中前进》","《日出》","《长江三日》","《荔枝蜜》"]
分子筛纯化系统为什么有时会发生进水事故，怎样解决？
