下列各组中的两组有机物不属于同分异构的是（ ）
A．葡萄糖与果糖
B．CH3CH2COOH和CH3COOCH3
C．正丁烷和异丁烷
D．淀粉和纤维素
A．葡萄糖与果糖分子式相同，结构不同，是同分异构体，故A错误；
B．CH3CH2COOH和CH3COOCH3分子式相同，结构不同，是同分异构体，故B错误；
C．正丁烷和异丁烷分子式相同，结构不同，是同分异构体，故C错误；
D．虽然淀粉与纤维素均可以用通式（C6H10O5）n表示，但在淀粉分子中，n表示几百到几千个单糖单元，在纤维素分子中，n表示几千个单糖单元，由于n值在二者分子中不相同，所以淀粉和纤维素不是同分异构体，故D正确．
故选D．
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| Helen 's favorite food is chocolate. Her parents and teacher often say that it's 1 for her teeth to eat too much chocolate. But she doesn't believe it. She often puts some chocolate in the milk for breakfast, the juice 2 lunch, even the soup for supper. Her mother has to 3 some chocolate in her bag before she goes to school. Sometimes when her mother goes shopping with her, Helen won't leave the shop 4 her mother buys some chocolate for her. The little girl 5 back from school with a painful(痛苦的) look yesterday afternoon. A tooth hurt and she had nothing. Her mother made some soup for her. But she put some chocolate in it. Her father bought some 6 for her, but she put some chocolate in it, too. Of course it was useless. 7 the next morning her mother took her to see the 8 .The dentist saw there was a cavity(洞) in her bad tooth . So he had to fill(填充) it with something. "Now, young girl," said the dentist , "what kind of filling(填充物) would you like for that tooth ?" " 9 , please," answered Helen. The dentist and Helen’s mother both laughed(大笑).The dentist asked Helen to eat fresh fruit and vegetables 10 chocolate. And It’s necessary for Helen to have healthy eating habits. | |||
| ( )1.A. good ( )2.A. for ( )3.A. get ( )4.A. when ( )5.A. go ( )6.A. medicines ( )7.A. But ( )8.A. doctor ( )9.A. Chocolate ( )10. A. instead | B.bad B.with B.put B.if B.came B.pills B.So B.nurse B.Milk B.but | C.well C.at C. buy C.until C.returned C.medicine C.And C.dentist C.Fruit C.instead of | |