Right answer: nochevieja
Noche Vieja (New Year's Eve), also called Víspera de Año Nuevo, Año Viejo or Fin de Año, is the last night of the year in the Gregorian calendar (the most widely used civil calendar in the world); this event lasts from December 31 to January 1.
During this celebration the people gather with friends and family to await the arrival of the New Year and rituals are performed, depending on the country, related to the expectations of next year.
Therefore the right option is a.