在婚礼上，他唱了一首专门为这个场合写的歌。

At the wedding, he sang a song written just for the ___occasion.

我有一套西装，但只在特殊场合穿。

I have a suit but I only wear it on special ___occasions.

恭喜你们结婚25周年纪念日。

Congratulations on the ___occasion of your 25th wedding anniversary.