Definition: In this task, you will be presented with a passage and have to answer a question based on your understanding of the events inferred from the passage. Try to find the best answer that is most likely to fill in "_". Note that the URLs in the text have been replaced with [Link].
Input: Cristiano Ronaldo is back on Portugal duty this week ahead of his country's crunch Euro 2016 qualifier clash against Serbia on Sunday night. Ronaldo was in the thick of the action at training following Real Madrid's 'El Clasico' defeat by Barcelona on Sunday night. The Catalans opened up a four-point lead over their arch rivals at the top of La Liga following their 2-1 victory at the Nou Camp. Cristiano Ronaldo (centre) takes on Ricardo Quaresma (left) and Vieirinha during training on Wednesday Ronaldo has a chat with Portugul head coach Fernando Santos during the session in Lisbon Ronaldo was waering his signature model Mercurial Superfly boots during the training sessionPortugal host Serbia in their Group I fixture in Lisbon on Sunday nightDenmark currently sit top of the Group on seven pointsVictory for Portugal on Sunday would stretch their gap over Serbia to eight points after four matches 
 Question:The Los Blancos star will have to put that defeat to the back of his mind, however, as Fernando Santos' side gear up for the visit of _.

Serbia