English Grammar it was an error/(a) that brought about/(b) his downfall./(c) no error/(d)

व्याख्या:- it was a error (mistake). There is overlap in the meaning. But while error simply means that something came out wrong, mistake implies that someone is to blame for it. As Dictionary.com defines it, a mistake is an error in action, calculation, opinion, or judgment caused by poor reasoning, carelessness, insufficient knowledge, etc.