“Rabbi, is it I?”

While Jesus was eating with the twelve disciples, he said to them, “Truly I tell you, one of you will betray me.”  Then the disciples were very sad and each one of them said to him, “Surely not I, Lord?”  But only Judas Iscariot said, “Rabbi, is it I?” (Matthew 26:20-25, Korean Modern Bible).  Why did Judas ask Jesus that?  Was it because he was pricked by his conscience?  If so, shouldn’t he have confessed, “Rabbi, it is I,” rather than asking, “Rabbi, is it I?”  How could Jesus “give thanks” for the bread in such a situation? (v. 26)  How could Jesus “give thanks” when he knew that he would be betrayed by his own disciple, Judas Iscariot (as it seemed he had already done) and be crucified?  I would like to confess my praise with faith by modifying the second half of the lyrics of the hymn “Nearer, My God, to Thee” verse 4 like this: ‘… until the time of my death, always giving thanks in prayer, I desire to draw nearer to the Lord.’