Option 1 (C), (A), (D), (B) -> Forms: "Just before the commencement of the examination, the invigilator instructed us to refrain from copying or indulging in any any other malpractices" - a grammatically correct and logical sentence.
Option 2 (A), (D), (C), (B) -> Places the time phrase awkwardly in the middle, disrupting sentence flow and meaning.
Option 3 (D), (A), (B), (C) -> Begins with a verb without proper subject placement, creating a grammatically incorrect structure.
Option 4 (B), (C), (D), (A) -> Starts with "or indulging..." which cannot begin a sentence, making it completely incoherent.
Hence, Option 1: (C), (A), (D), (B) -> The sentence follows proper English structure with the time adverbial phrase at the beginning, followed by subject (the invigilator), verb (instructed), and object with complete action description (refrain from copying or indulging in malpractices) -> correct