Different between congratulations and congratulation. and when to use them?

The difference between congratulations and congratulation, is congratulations is used when you want to praise someone directly on an occasion. for example, congratulations would be used when you say, “congratulations on your promotion!” meanwhile, congratulation is a noun that indicates an expression of a praise/congratulating someone, but doesn’t directly express congratulation. for example, congratulation could be used in, “people threw a party in congratulation for her promotion.” the ‘s’ at the end expresses well wishes

What are the options for your question

It could be c or d but most likely c