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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
【单选题】有一汽轮机工作于500℃及环境温度为30℃的条件下，若该热机从热源吸热10000kJ，则产生的净功为（）kJ。
A.
6 258
B.
5 826
C.
5 800
D.
6 080