Explanation

• the whole was behind the resident.
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• 'behind' preposition is used at or to the back of someone or something:
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• Behind is best to keep the meaning of the original sentence
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• behind is a preposition of place so we use the "behind" preposition because they indicate the place
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• some Prepositions of place are  (in, on, at, next to, in front of, behind, under, etc.)