【简答题】2011年我国女科学家屠呦呦发现青蒿素(青蒿素的化学式:C 15 H 22 O 5 ),它是一种用于治疗疟疾的药物,获美国拉斯克奖. (1)一个青蒿素分子含有______个原子. (2)青蒿素分子中C、H、O三种元素的质量比为______. (3)5g青蒿素中含有氧元素的质量为______.
【单选题】The total revenue test says i) Demand is elastic if a decrease in price results in an increase in total revenue. ii) Total revenue is maximized when demand is elastic. iii) Total revenue is minimized ...