OnSundays there were a lot of children playing in the park parents seated together joking

问题补充：

OnSundays there were a lot of children playing in the park, parents seated together joking.

A. whose

B. their

C. which

D. where

答案：

A. whose

(答案→)B. their

C. which

D. where

解析：考查独立主格。句义：在星期天，有许多孩子在公园里玩，家长们坐在一起开着玩笑。把握逗号后的非谓语动词seated，这是关键词，由此确定是非谓语，而不是从句，所以A ＣD都不对，所以B正确。