她的情绪似乎在快乐和忧郁之间交替。

Her mood seems to ___alternate between cheerfulness and melancholy.

这家咖啡馆每周轮换特色饮品。

This cafe ___alternates its featured drink every week.

他写作时，会在集中工作和短暂休息之间交替。

When he writes, he ___alternates between intense work and short breaks.