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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】中间不完全冷却的双级蒸汽压缩式制冷循环是指（）。
A.
冷凝液体从冷凝压力到蒸发压力先后经过两个节流阀
B.
将低压压缩机的排气冷却到中间压力下的饱和温度后进入高压压缩机
C.
将低压压缩机的排气冷却，但未冷却到中间压力下的饱和温度
D.
没有将低压压缩机的排气冷却到冰点