Part A
The most appropriate answer is C. She is furious about what Mr. Van Daan has just been caught doing. In this scene, Mrs. Frank's anger is specifically directed towards Mr. Van Daan after discovering he has been stealing food from the group.
Part B
The quotation that best supports the answer to Part A is C. "Your own son Peter . . . I’ve heard him moan in his sleep, he’s so hungry. And you come in the night and steal food that should go to them . . . to the children!" This quotation illustrates Mrs. Frank’s outrage over Mr. Van Daan's actions and highlights the moral implications of his behavior, directly supporting her decision to order them to leave.