问题补充：
Do you know last Sunday?
A. where they had a picnic
B. where did they have a picnic
C. where they have a picnic
D. where will they have a picnic
答案：
(答案→)A. where they had a picnic
B. where did they have a picnic
C. where they have a picnic
D. where will they have a picnic
解析：句意：你知道上个星期天他们在哪里野餐了吗？首先上个星期天，句子判断用一般过去时，know之后引导是宾语从句，宾语从句用陈述句语序，故选A.
