Read the sentence to find out whether there is any grammatical or idiomatic error in it. The error, if any, will be in one part of the sentence. The corresponding letter of that part is the answer. If the given sentence is correct as it is, then choose option ‘No Error’ as your answer response. (Ignore errors of punctuation, if any).

Many aspects concern Indian politics(A)/ have seen changes, and many previous concepts(B)/ have been rendered obsolete, though leaders and parties (C)/still find it difficult to shake off their past beliefs (D).