Today, however, Daddy's with him. That means Mommy can answer Laura in peace!
Anyway, in order to understand the answer, I must first explain what the Triduum is. For Catholics, the Triduum is the holiest time in our Liturgical Calendar. It is the most important part of Salvation History as Christ, in those three days, fulfilled the promise of God when He said He would send a Savior who would reconcile humanity to Himself.
The Triduum, thus, becomes Holy Thursday Mass (when we remember the Last Supper), Holy Saturday (when we remember Christ's descent into Hell), through the Easter Vigil and Easter celebrations (when we remember His Glorious Resurrection and triumph over Death).
Anyway, since this is the most sacred part of the year for the Church - the finite point in linear history that somehow encapsulates the timeless Sacrifice of Christ - our Liturgy reflects our solemn, adoring and anguished spirit. We see ourselves, the Church, as dying WITH Christ.
This is also why throughout Lent, things are slowly removed from our Masses. Statues are draped (or even removed), fewer candles are lit, our beautiful "Alleluia" is laid to rest, and floral arrangements are typically absent.
As I explained to my children, something very special happens after Holy Thursday Mass. The priest removes Christ from the tabernacle and processes with Him to a place of repose. This signifies that Christ has begun His Sacrifice (which truly did begin with the moment of Consecration at the Last Supper - more on that in a bit).
The Mass on Holy Thursday does not "end." There is no "Go forth" or "Thanks be to God." There is only the procession of Christ to His place of repose and the silent, prayerful adoration of the faithful that stay watch with Him as He endures His Passion (akin to the Apostles as Christ led them to the Garden of Gethsemane to keep watch as He began His Agony in the Garden).
In fact, to further this point, after the Procession, the Church is stripped bare. Linens are removed from the pulpit, altar, tabernacle, etc. Furniture (like chairs, microphones, lecterns, etc) are taken into the sacristy. Candles aren't just snuffed out - they are removed entirely. Carpets are rolled away. Remaining statues may be taken down. Every movable object is taken away from our sanctuary and all lights (be they candles, spot-lights or chandeliers) are deadened. Our Church, symbolic of the spirit of all the faithful who create Her, dies with Her Master. He who is the Light of the World is consenting to become obscured and entombed.
As His faithful Spouse, we acknowledge our desolation... our mourning... our grief.
On Good Friday, there is "no Mass." Again, this is because technically, the Mass from Holy Thursday has not ended - nor will it until the close of the Vigil on Holy Saturday. Instead, we continue the Mass through Stations of the Cross, Adoration, communal and private meditation, recitation of the Rosary (specifically the Sorrowful Mysteries), Tenebrae etc.
This is to signify that we, the Church, the faithful Bride of Christ, follow Him on His Path towards Salvation. We consent to die with Him in order to take part in His Resurrection.
This moves us to Holy Saturday. On Holy Saturday, we remember in a special way Christ's descent into Hell, Limbo and Purgatory. We remember His Triumphant opening of the Gates of Heaven that were closed against us as a result of Original Sin. There is actually no "liturgy" for Holy Saturday until the vigil. This is a continuation of Christ's Sacrifice which began during Holy Thursday.
Finally, we arrive at our Easter Vigil. This special vigil is held after sundown. This is significant because this darkness is indicative of the spiritual darkness we are experiencing as we await the Light of the World. Again, this vigil does not start with the typical "opening Mass prayers" we're used to. Instead, the priest blesses a special fire which is typically made of Holy Oils from the previous year, salt, and twigs. This special fire is the first light we see and is symbolic of the Resurrection. This light is what's used to light our brand new Paschal Candle (the Christ Candle), and after the Candle is lit, the light begins to spread throughout the Church, from member to member, as a flame is passed between individual candles all are given at the opening of Mass.
As a sacristan who has been at the front of the Church awaiting the Exsultet (when we flip on all the lights, light all the candles, and bust out all the finery we've got to offer), seeing this light slowly spread throughout the entire Church... it's incredible.
Anyway, this is the point in the Liturgical Calendar in which we celebrate and acknowledge Christ's Triumph over Death. The Sacrifice has been complete and Salvation has been granted to us. Through His Offering, we have become reconciled and all the promises of God the Father to His Creation regarding the Messiah have been fulfilled. We rejoice in being reborn through His Death and Resurrection.
As THIS VIGIL MASS commences, we finally are able to hear again the priest's command to "Go Forth" and respond with a jubilant "Thanks be to God!" We acknowledge that the sacred Triduum that marks Christ's Sacrifice has reached its fulfillment, and we take our charge to "Go Forth" with zeal. We are charged to take the message of Salvation to all people who still "live in darkness."
So that, dear Laura, is why the answer to number 11 on the test was "One." There is but one Mass celebrated over 3 days during the Triduum.
As these three days recall the three long days of Christ's consummation by the Fire of His Love, we, too, offer these three days in solidarity with Him.