The true sentence is the following one:
B. Individual productivity is necessary for group productivity.
Imagine a work in a group, where the people all receive their personal tasks that they will later incorporate into the group work. If each person is not productive on their own task then the whole group will not be productive!
By giving you explained details and using defining word and How the author used specific names.
Throughout the horrors of his captivity, Wiesel states that he needed to be strong for his father. He needed to survive for his father. After his father's death, he no longer feels as though he has anything to live for. It can be assumed that he no longer paid attention to the world around him. His lack of detail about that is due to the fact that he no longer cared about what was going on.