We'll have a picnic in the park this Sunday it rains or it's very cold.A. sinceB. ifC. un

问题补充：

Well have a picnic in the park this Sunday it rains or its very cold.

A. since

B. if

C. unless

D. until

答案：

A. since

B. if

(答案→)C. unless

D. until

解析：

句意：除非下雨或天很冷，我们将在本周日去公园野餐。从句子之间的逻辑关系判断此处应为否定条件句，相当于if...not，故排除if，而选unless。A项since表因果关系。D项until只能引导时间状语从句，故排除。