C:

The Sluzebnik does not specify the verses of the Psalms or mention or give the text for the hymn O Only-begotten Son ....  The 1965 Liurgikon gives three, thus:

 

SECOND ANTIPHON[59]

SUNDAY

WEEKDAY

Be gracious to us, O God, and bless us; let Your face shine upon us, and have mercy on us.

O Son of God, risen from the dead, save us who sing to You. Alleluia.

That Your way may be known upon earth, among all nations Your salvation.

O Son of God, risen from the dead, save us who sing to You. Alleluia.

Let the peoples praise You, O God, let all the peoples praise You.

 

O Son of God, risen from the dead, save us who sing to You. Alleluia.

The Lord reigns, He is clothed in majesty; robed is the Lord and girt about with strength.

Through the prayers of Your saints, O Savior, save us.

 

For He has made the world firm, which shall not be moved.

Through the prayers of Your saints, O Savior, save us.

Your decrees are worthy of trust indeed; holiness befits Your house, O Lord, for length of days.

Through the prayers of Your saints, O Savior, save us.

See also the  Apostol which indicates three verses and the Hymn of the Incarnation (without giving the full text for the latter).

 

Glory be to the Father, and to the Son and the Holy Spirit, now and ever, and forever. Amen. O only-begotten Son and Word of God, Who, being immortal, deigned for our salvation to become incarnate of the holy Mother of God and ever-Virgin Mary, and became man without change; You were also crucified, O Christ, our God, and by death have trampled Death, being One of the Holy Trinity, glorified with the Father and the Holy Spirit, save us.