问题
选择题
Lucy's birthday party didn't start _____ all the friends arrived. [ ]
A. since
B. until
C. while
答案
答案：B
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Lucy's birthday party didn't start _____ all the friends arrived. [ ]
A. since
B. until
C. while
答案：B
Na2S(s)+4H2O(g)。下列说法正确的是