Bible Mystery- Who replaced Judas?

Act 1:20  For it is written in the book of Psalms, Let his habitation be desolate, and let no man dwell therein: and his bishoprick let another take.

• 12 Apostles\
• Luk 6:12  And it came to pass in those days, that he went out into a mountain to pray, and continued all night in prayer to God. 
  Luk 6:13  And when it was day, he called unto him his disciples: and of them he chose twelve, whom also he named apostles; 
  Luk 6:14  Simon, (whom he also named Peter,) and Andrew his brother, James and John, Philip and Bartholomew, 
  Luk 6:15  Matthew and Thomas, James the son of Alphaeus, and Simon called Zelotes, 
  Luk 6:16  And Judas the brother of James, and Judas Iscariot, which also was the traitor. 
• Acts 1:10-22
• Acts 1:24-25
• We hear so little of