题目

Although there is a difference in spelling and pronunciation between American English and British English, both of the countries have much to _______. A. communicate        B . change     C. share      D. improve   答案：C11．现有①液态氧，②碳酸氢铵，③铜，④水，⑤洁净的空气，⑥干冰，六种物质中（填写编号）（1）混合物是⑤；（2）单质是①③；（3）化合物是②④⑥；（4）氧化物是④⑥．