The correct answer is 'investigation.' Key Points - Let us see the meaning of Reconnaissance: - Reconnaissance: military observation of a region to locate an enemy or ascertain strategic features, investigation. , - Example: Spotter planes made a preliminary aerial reconnaissance of the island. - Let us see the meanings of the given options: - Revaluation: the action of assessing the value of something again. - Ratification: the action of signing or giving formal consent to a treaty, contract, or agreement, making it officially valid. - Investigation: the action of investigating something or someone; formal or systematic examination or research. - Regularisation:the act of changing a situation or system so that it follows laws or rules, or is based on reason. - From the meanings of the given words, we cansay that the word 'investigation' is nearest in meaning to the underlined word 'reconnaissance'. - Hence, the correct answer is 'investigation.'