A & B, Without the Benefit of Marriage Lived Together

A & B, without the benefit of marriage lived together as husband and wife. They begot C. A, the father adopted C to elevate him to the status of legitimacy. What is the middle name of the child?

A) C has no middle name because there is no law on middle name.
B) C carries the surname of his biological mother because of customs and traditions of Filipinos.
C) C carries the surname of his biological mother inorder not to make it difficult for him to prove relationship to her when the issue of succession will arise.
D) C carries the middle name of his adopting father.