One of the choices Elie has to make toward the end of the book is when he is in the hospital ward because of an infection in his foot. They hear the rumblings of Allied bombs dropping and learn the camp is to be evacuated.
Elie and his father need to decide whether or not to go or stay behind. Due to various accounts of what happens, Elie is nervous to stay behind because he believes it will lead to both of them being killed. So he and his father decide to evacuate with the others. Elie goes on to say that he found out later in his life, had they stayed in the camp, the Allies showed up shortly after the evacuation and liberated the camp. Had they only stayed behind, they would have been free and his father would have survived.
Assuming that you mean when Elie's father is near death, Elie struggles with whether to follow another prisoner's advice to take and eat his father's food in addition to his own. The reasoning is that Elie's father is most certainly dying, and the extra food might sustain a healthier Elie.
However, this decision is extremely difficult because Elie's relationship with his father has changed drastically. He goes from being embarrassed and rather ashamed of his father (because of his dad's inability to march or preserve himself) to trying to motivate his father through one more day and night. As Elie has just reconciled himself to the fact that he desperately wants his dad to live, Chlomo's condition worsens.
Elie decides to take care of his father as best as possible. He is a caring "nurse" to his dad in his last hours and puts himself second when it comes to his own needs. Unfortunately, Chlomo passes away, and Elie is so emotionally and physically drained that he cannot cry at his father's death. He almost feels "a sense of relief."