In the following question, one part of the sentence may have an error. Find out which part of the sentence has an error and click the button corresponding to it. If the sentence is free from error, click the ''No error'' option.  A man can fail many times, (A)/ but he isn't a failure unless he (B)/ begins to blame somebody else. (C)/ No error (D)?

Option 2 : B 

The correct answer is B

• Here, we must use until because it is used to denote a time constraint upon something or to simply denote time. Here we are talking about ''failing many times'' but ''real failure being the time one blames others.'' 
• So the usage of "Until" is wrong it is used for "time reference" use "Unless" for conditions. 
• Let's see some examples with the help of the table:

  Until(Up to the point of time or event mentioned)	Unless(used to introduce the case in which a statement being made is not true or valid) or for conditional sentences.
  For example, You couldn't vote until you're 18	For example, Unless he begs pardon, they won't forgive him.

So according to the above table, the correct sentence is: A man can fail many times, but he isn't a failure until he begins to blame somebody else.