evanescent

彩虹的美是转瞬即逝的，几分钟后就消失了。

The beauty of a rainbow is ___evanescent, disappearing after just a few minutes.

茉莉花转瞬即逝的香气飘过花园，几秒后就消散了。

The ___evanescent fragrance of jasmine drifted through the garden and was gone in seconds.

他回望过去，才发现大学时光原来如此短暂易逝。

He looked back and realized how ___evanescent his college years had been.