이 오류는 어디서 발생하는건가요?

index.js:1 Warning: Encountered two children with the same key, `1`. Keys should be unique so that components maintain their identity across updates. Non-unique keys may cause children to be duplicated and/or omitted — the behavior is unsupported and could change in a future version.

    in select (at UploadProductPage.js:68)

    in form (created by Context.Consumer)

    in Form (at UploadProductPage.js:49)

    in div (at UploadProductPage.js:43)

    in UploadProductPage (at auth.js:38)

    in AuthenticationCheck (created by Context.Consumer)

    in Route (at App.js:24)

    in Switch (at App.js:20)

    in div (at App.js:19)

    in Suspense (at App.js:17)

    in App (at src/index.js:29)

    in Router (created by BrowserRouter)

    in BrowserRouter (at src/index.js:28)

    in Provider (at src/index.js:21)