On Sundays there were a lot of children playing in the park, _______ parents seated together joking.
A. their B. whose
C. whichD. that
【陷阱】容易误选B，认为这是非限制性定语从句。
【分析】最佳答案是A。与上面一题相似，their parents seated together joking 不是非限制性定语从句，而是一个独立主格结构，因为空格后的动词 seated 不是谓语，而是一个过去分词，因为 seat 作动词用时，是及物动词。比较以下相似题：
(1) On Sundays there were a lot of children playing in the park, _______ parents were seated together joking.
A. theirB. whose
C. whichD. that
选B。whose parents were seated together joking 为非限制性定语从句，因为其后有完整的谓语 were seated。
(2) On Sundays there were a lot of children playing in the park, and _______ parents were seated together joking.
A. their B. whose
C. whichD. that
选A。因为句中有并列连词and，整个句子为并列句。
(3) On Sundays there were a lot of children playing in the park, _______ parents sitting together joking.
A. theirB. whose
C. whichD. that
选A。their parents sitting together joking 为独立主格结构。
(4) On Sundays there were a lot of children playing in the park, _______ parents sat together joking.
A. their B. whose
C. whichD. that
选B。whose parents sat together joking 为非限制性定语从句，因为句中有完整的谓语 sat。
(5) On Sundays there were a lot of children playing in the park, _______ parents were sitting together joking.
A. theirB. whose
C. whichD. that
选B。whose parents were sitting together joking 为非限制性定语从句，因为句中有完整的谓语 were sitting。
