---What are you going to do this weekend ?Well we’ll clean up the city parks it rain

问题补充：

---What are you going to do this weekend ?

--- Well, we’ll clean up the city parks it rains..

A. if

B. until

C. while

D. unless

答案：

A. if

B. until

C. while

(答案→)D. unless

解析：句意：这个周末你们要做什么？如果不下雨的话我们要打扫城市公园。unless 除非，如果不，相当于if not;根据句意，故选D。