The word “scenario” is related to the Latin word “scena” which means “scene,” but in Latin the “c” made the [k] sound. Over time, the [k] sound was dropped but Latin based words retained their “sc” spelling. So, technically the “c” is silent and the “s” is not. It is still included even though we don’t say it. This happens a lot in English where the pronunciation of older words have changed, but the spelling has remained relatively the same. Now, you don’t have to worry about it anymore. Have a nice day.