the plumber went up the _____ to the top floor

The child's question: the plumber went up the _____ to the top floor

In Russian, the missing word is "лестнице" (lestnitse), which means "stairs". So, the sentence would be: "Сантехник поднялся по лестнице на верхний этаж." (The plumber went up the stairs to the top floor.)

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