【判断题】正常运行的管道,突然关阀会造成管内产生增压波。因此,关阀的速度越慢越好。
【简答题】898×9≈______ 403×6≈______.
【简答题】进制转化:403 (6)= ______ (8) .
【单选题】A clean environment can help the city bid for the Olympic, which __________ will promote its economic development. [ ]
【简答题】估算:21×403≈______7413÷62≈______.
【简答题】169×28≈______ 403×18≈______.
【简答题】口算. 82+258= 24×60= 840÷20= 860-403= 58×0= 320÷20= 22+508= 125-25×0= 420÷15= 25×6×4= 65-15×2+3= 75-6×(1+4)=
【多选题】下列聚合物是共聚物( copolymer )的是
A.
氯乙烯-醋酸乙烯共聚物(Ethylene-vinyl acetate copolymer)
B.
聚己二酰己二胺(Polyamide -66,Nylon 66, PA-66)
C.
丁二烯苯乙烯(Polybutadiene-styrene ,PBS)
D.
丁苯橡胶(Polymerized styrene butadiene rubber ,SBR)
【单选题】A clean environment can help the city ________ the Olympics, which in turn will promote its economic development. [ ]
【多选题】下列聚合物中结构单元(Structural unit)、重复结构单元(Structural repeating unit)、单体单元(Monomer unit)相同的是
B.
聚氯乙烯(Polyvinyl chloride,PVC)
C.
聚己二酰己二胺(Polyamide 66,PA66)
D.
聚甲基丙烯酸甲酯(Polymethyl methacrylate,PMMA)