Why is the Church one, holy, catholic, and apostolic?

This is an excerpt from today's News.va (link below):

Why is the Church one, holy, catholic, and apostolic?

Dear friends, we just thought to share with you some fundamental notions from the (Compendium of the) Catechism of the Catholic Church on this question...

161. Why is the Church one?

The Church is one because she has as her source and exemplar the unity of the Trinity of Persons in one God. As her Founder and Head, Jesus Christ re-established the unity of all people in one body. As her soul, the Holy Spirit unites all the faithful in communion with Christ. The Church has but one faith, one sacramental life, one apostolic succession, one common hope, and one and the same charity.

162. Where does the one Church of Christ subsist?

The one Church of Christ, as a society constituted and organized in the world, subsists in (subsistit in) the Catholic Church, governed by the Successor of Peter and the bishops in communion with him. Only through this Church can one obtain the fullness of the means of salvation since the Lord has entrusted all the blessings of the New Covenant to the apostolic college alone whose head is Peter.

163. How are non-Catholic Christians to be considered?

In the churches and ecclesial communities which are separated from full communion with the Catholic Church, many elements of sanctification and truth can be found. All of these blessings come from Christ and lead to Catholic unity. Members of these churches and communities are incorporated into Christ by Baptism and we so we recognize them as brothers.

164. How does one commit oneself to work for the unity of Christians?

The desire to restore the unity of all Christians is a gift from Christ and a call of the Spirit. This desire involves the entire Church and it is pursued by conversion of heart, prayer, fraternal knowledge of each other and theological dialogue.

Source: http://bit.ly/1nqfsBd

Fresco from the Catacomb of Saints Peter and Marcellinus in Rome, dating to the 5th century, showing Christ, Sts Peter and Paul.