To what did the "credibility gap" refer?

Read the following passages. passage a: we who lived in concentration camps can remember the men who walked through the huts comforting others, giving away their last piece of bread. they may have been few in number, but they offer sufficient proof that everything can be taken from a man but one thing: the last of human freedoms - to choose one's attitude in any given set of circumstances - to choose one's own way. passage b: for as long as political life has existed in germany, there has never been a movement such as ours. created from nothing and embracing people of all regions, all classes, all professions, all heritages. they can oppress us; they can even kill us. but we will never surrender. passage c: who am i? they also tell me/ i bore the days of misfortune/ equably, smilingly, proudly, /like one accustomed to win. passage d: a democratic government did nothing to stem the flow of high inflation and unemployment that seemed to grow worse week by week. people grew desperate for change. which passage offers the truest belief of nazism in germany? passage b passage d passage a passage c