C. Decrescendo would be an appropriate choice to reflect the mood when the ice cream van interrupts the wedding ceremony. A decrescendo is a musical term that refers to a gradual decrease in volume, which can be used to convey a sense of interruption or distraction. By having the music gradually become softer, you can create a sense of disruption and a break in the moment, which could reflect the mood when the ice cream van interrupts the wedding ceremony.