In the following question, a sentence is given with a phrase highlighted in bold. Find out the phrase, among the phrases (a, b, c,
d) given below each sentence, which should replace the phrase printed in bold to make the sentence grammatically correct. If the sentence is already correct, mark (5),
i.e. 'No correction required', as the answer. My correspondents, mostly strangers, were polite but insistent; they wanted my take on a theory, newly circulating online, that offered a resolution to one of the most allurement digital mysteries of the past decade, the real identity (or identities) behind the persona of Satoshi Nakamoto.