Transform the below sentence by replacing the word-"if" with the most appropriate word:
If I were the Prime Minister, I would have eradicated all health issues in the country.
Option A: The auxiliary verb, 'had' can be used to replace the word' if' in a conditional sentence in the past tense. The given sentence is in the past tense.In such a case, the word 'if' can be omitted and the sentence can be transformed by inverting the position of the subject and the auxiliary verb, 'had'. In the given sentence, the subject is 'I'. The clause, 'If I were the Prime Minister' can be re-phrased as: 'Had I been the Prime Minister'. Hence, Option A is correct.
Option C: The word, 'unless' is used to replace 'If... not'. In the given sentence, the word, 'not' isn't used. Hence, this option is incorrect.
Option D: 'Whether' is a conjunction which is used to express a choice between two alternatives or events. Here, there is no such reference. Hence, this option is incorrect.