On Sundays there were a lot of children playing in the park, parents were sitting together joking.
A. their
B. whose
C. which
D. that
网友回答
A. their
(答案→)B. whose
C. which
D. that
解析：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。