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刷刷题刷刷变学霸
举一反三
【单选题】Most shoppers know the feeling. You stand in front of piles of organic produce and wonder what those premium prices are buying you over and above what you get from standard foods. Not a lot nutrition-...
A.
do not use naturally produced fertilisers
B.
produce carbon dioxide when removing weeds
C.
use high doses of weed-killer
D.
use too many resources to qualify for organic status
【多选题】回热加热器水位过低,对机组运行的影响有()
A.
可能引起疏水带汽进入下一级加热器,排挤更多的低压抽汽,降低热经济性
B.
疏水管道中汽水两相流动,对疏水阀及疏水管弯头产生严重冲蚀
C.
可能引起疏水带汽进入下一级加热器,减少的低压抽汽,提高热经济性
D.
加热器端差增加,影响机组的经济性