1 mol X能与足量碳酸氢钠溶液反应放出44.8 L CO2(标准状况),则X的分子式是( ) A.C5H10O4 B.C4H8O4 C.C3H6O4 D.C2H2O4 答案:D 解析:1 mol X能与足量碳酸氢钠溶液反应放出44.8 L CO2(标准状况),说明X中含有2个—COOH,饱和的二元羧酸的通式为CnH2n-2O4,当为不饱和时,H原子个数小于2n-2,符合此通式的只有选项D。
-- Are you still ______ the book?
-- No, I'm ______ to do my homework.[
]A. reading, begining B. reading, beginning
C. readding, beginning D. readding, begining