Catechism of the Catholic Church
All of the above. Para. 503: Mary's perpetual virginity manifests God's absolute initiative in the Incarnation. Jesus has only God as Father. . . .
Para. 504: Jesus is conceived by the Holy Spirit in the Virgin Mary's womb because he is the New Adam, who inaugurates the new creation: "The first man was from the earth, a man of dust; the second man is from heaven" (1 Cor 15:45, 47).
Para. 505: By his virginal conception, Jesus, the New Adam, ushers in the new birth of children adopted in the Holy Spirit through faith. "How can this be?" (Lk 1:34; cf. Jn 3:9) Participation in the divine life arises "not of blood nor of the will of the flesh nor of the will of man, but of God" (Jn 1:13).
Para. 506: Mary is a virgin because her virginity is the sign of her faith "unadulterated by any doubt," and of her undivided gift of herself to God's will (LG 63; cf. 1 Cor 7:34-35).