The price elasticity of demand for hamburger is______.
A. the change in the quantity demanded of hamburger when hamburger increases by 30 pence per pound
B. the percentage increase in the quantity demanded of hamburger when the price of hamburger falls by 1 per cent per pound
C. the increase in the demand for hamburger when the price of hamburger falls by 10 per cent per pound
D. the decrease in the quantity demanded of hamburger when the price of hamburger falls by 1 per cent per pound
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物流是赢得竞争性优势的重要源泉。
A. 正确
B. 错误
脑复苏时。为防止脑组织发生不可逆损伤，脑循环血量最低应保持在
A. 25%
B. 20%
C. 10%
D. 0.15
E. 0.05
Morning people have ______ early in the day.
A. a meeting
B. much work to do
C. exercise to do
支气管肺炎一般用鼻前庭导管氧浓度不超过
A. 10%
B. 20%
C. 50%
D. 0.4
E. 0.6
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