The correct answer is 'A'. Key Points The sentence is erroneous because ‘HAVE’ is present in the 'A' part. 'have protested' should be replaced by 'protested' THE WORDS LIKE- last/past, the day before yesterday, adverb of past time, etc, when present in any sentence it should be expressed in ‘simple past tense’ The simple past (also called past indefinite) is a verb tense that is used to show that a completed action took place at a specific time in the past. Example: I went to the park Structure: Sub + V2 + object Hence, the 'last year' of the sentence suggests that the sentence should be converted to past indefinite tense. Therefore 'have' will be removed. Additional Information You must always use the present perfect when the time of an action is not important or not specified. You must always use the simple past when details about the time or place that an action occured are given or requested. Past continuous Sub + was\were + Verb(ing) + Object He was going to college. Past perfect Sub + Had + verb(3rd form) + Object He had completed his graduation. Past perfect continuous Sub + Had + been + verb(ing) + Object + Since/For + Time I had been waiting for you since morning Correct sentence-‘Old people protested in the capital last year, complaining that the central government pension of 200 hundred rupees a month has been frozen since 2007.'