________ the local municipal council acted decisively to repair the cracked retaining wall last season, the lower residential valley would be completely flooded right now.Choose the correct word to complete the negative inverted conditional sentence.

Answer: B. Had not

The council did repair the wall, so the valley is not flooded; the sentence imagines the opposite, so it needs a negative condition. In a formal inverted conditional the auxiliary comes first and is not contracted: "Had not the council acted..." (= If the council had not acted...). "Hadn't" cannot be used in inversion, and "Had" alone would reverse the meaning.

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