她平静的微笑立刻让我放松下来。

Her ___serene smile immediately put me at ease.

艺术家捕捉到了对象脸上完全平静的表情。

The artist captured a completely ___serene expression on the subject's face.

冥想后，他的内心感到平静而清晰。

After meditating, his mind felt ___serene and clear.