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The students will put off the outing until next week， ________ they won’t be so busy.
A、when
B、as
C、since
D、while
【正确答案】：A
【题目解析】：“they won't be so busy”说的是下周的情况，即they won't be so busy next week，可知next week这个时间名词在后句中作时间状语，填入后引导定语从句。