alternate/ˈɔːltɜːneɪt/
vt., vi.-nated, -nating1. （常与with连用）（使）轮流2. （与between连用）（使）交替alternated between hope and fear处于希望与恐惧之中
His life seems very dull and alternates between work and sleep.他的生活似乎很枯燥，就是工作完了睡觉，睡完觉又工作。
The weather alternates between sunshine and rain.时而天晴，时而下雨。