solemn的名词形式是什么

　　例句：

　　I made a solemn promise that I would return.

　　我郑重承诺我会回来的。

　　His behaviour was not in keeping with the solemn occasion.

　　他的举止与这庄严的场合不协调。

　　This is a solemn curtsy in the party.

　　这是一个在聚会中的隆重的礼节。