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【多选题】
关系代数的基本运算有哪些?A.
并
B.
差
C.
笛卡尔积
D.
投影
E.
选择
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【单选题】In his essay 'The Parable of the Tapeworm,' Mario Vargas Llosa argues that at the heart of the writer's will to write is rebellion, a 'rejection and criticism of life as it is.' Moreover, he speculate...
A.
both of them are portable.
B.
both of them are difficult to govern.
C.
both of them can be used in rebellion.
D.
both are them are highly influential.
【单选题】稀释与接种法测定水中BOD 5 时,下列水样应进行接种的是( )。
A.
污水处理厂的出水
B.
含有城镇污水的河水或湖水
C.
不含或只含很少量微生物的工业废水
D.
未受工业废水污染的生活污水
【单选题】稀释与接种法测定水样中BOD5时，对稀释水的要求错误的是( )
A.
控制水温(20±1)℃
B.
使用前加入一定量四种盐溶液混匀
C.
溶解氧达到饱和
D.
稀释水的pH值应在6.5-7.5之间
E.
稀释水BOD5的测定结果不超过0.5mg/L
【简答题】稀释与接种法测定水中BOD5时，如水样为含难降解物质的工业废水，可使用（）的稀释水进行稀释。
【单选题】In his essay 'The Parable of the Tapeworm,' Mario Vargas Llosa argues that at the heart of the writer's will to write is rebellion, a 'rejection and criticism of life as it is.' Moreover, he speculate...
A.
both of them are portable.
B.
both of them are difficult to govern.
C.
both of them can be used in rebellion.
D.
both are them are highly influential.
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