classroom is cleaner than A. Our; theirB. Our; theirsC. Their; ourD. Theirs; ours.

问题补充：

classroom is cleaner than

A. Our; their

B. Our; theirs

C. Their; our

D. Theirs; ours.

答案：

A. Our; their

(答案→)B. Our; theirs

C. Their; our

D. Theirs; ours.

解析：此题重点考查形容词性的物主代词和名词性的物主代词的根本区别。名词性的物主代词就相当于形容词性的物主代词+名词。