Find the part of the sentence that contains an error: The complaint letters that were received through email (1)/ and verified by the clerk (2)/ are being files systematically (3)/ in separate folders. (4)

Explanation

The correct option is (c). Option (c) contains an error. Detailed explanation of error: The phrase “are being files” is grammatically incorrect because after “are being” (present continuous passive structure), we must use the past participle (V3) form of the main verb. The verb intended here is “file” (to arrange documents in folders). The correct past participle is “filed”, not “files”. Hence, the correct phrase should be “are being filed systematically”. Correct sentence: The complaint letters that were received through email and verified by the clerk are being filed systematically in separate folders. Grammatical rule used: Present Continuous Passive = am/is/are + being + V3. Example: The reports are being checked by the manager. Information booster: In passive voice, always ensure the main verb appears in V3 (past participle). Using the base form or present form after “being” leads to a direct grammar error. So the correct answer is (c)