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【单选题】
下列滤器中能用于终端滤过的是（ ）A.
砂滤棒
B.
板框压滤机
C.
钛棒过滤器
D.
微膜器
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举一反三
【单选题】.制定劳动定额的方法有很多,用测时、观察、实验等手段,测定每作量,据以制定定额的一种方法是()。
A.
.技术测定法
B.
.经验估计法
C.
.统计分析法
D.
.比较类推法
【单选题】制定劳动定额的方法有很多用潮时、观察、实验等手段,测定每劳动过程的标准时间及其平均完成的工作量,据以制定定额的一种方法是()
A.
技术制定法
B.
经验告计法
C.
统计分析法
D.
比较类推法
【单选题】制定劳动定额的方法有很多,用测时、观察、实验等手段,测 动 过 程 的 标 准 时 间及其平均完成的工作量,据以制定定额的一种方法是()。
A.
. 技术测定法
B.
. 经验估计法
C.
. 统计分析法
D.
. 比较类推法
【多选题】What is nitrogen cycle?
A.
In the biosphere, the metabolic processes of different species function interdependently to salvage and reuse biologically available nitrogen in a vast nitrogen cycle.
B.
The first step in the cycle is fixation (reduction) of atmospheric nitrogen by nitrogen-fixing bacteria to yield ammonia (NH 3 or NH 4 + ). Although ammonia can be used by most living organisms, soil bacteria that derive their energy by oxidizing ammonia to nitrite (NO 2 ˉ ) and ultimately nitrate ( NO 3 ˉ) are so abundant and active that nearly all ammonia reaching the soil is oxidized to nitrate. This process is known as nitrification.
C.
Plants and many bacteria can take up and readily reduce nitrate and nitrite to ammonia through the action of nitrate and nitrite reductases. This ammonia is incorporated into amino acids by plants. Animals then use plants as a source of amino acids to build their proteins. When organisms die, microbial degradation of their proteins returns ammonia to the soil, where nitrifying bacteria again convert it to nitrite and nitrate.
D.
A balance is maintained between fixed nitrogen and atmospheric nitrogen by bacteria that reduce nitrate and nitrite to N 2 under anaerobic conditions, a process called denitrification. These soil bacteria use NO 3 ˉ or NO 2 ˉ rather than O 2 as the ultimate electron acceptor in a series of reactions that (like oxidative phosphorylation) generates a transmembrane proton gradient, which is used to synthesize ATP.
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