Answer: LOAD_UNCERTAIN_FILES

The question specifically asks for the COPY INTO option that loads files with expired load metadata while attempting to avoid data duplication. LOAD_UNCERTAIN_FILES (option A) is the correct choice because it references load metadata when available to prevent duplication, but also attempts to load files with expired metadata. This balances the need to load potentially new data while minimizing duplication risk. FORCE (option B) loads all files regardless of metadata, which would cause duplication. VALIDATION_MODE (option C) is for testing load operations without actually loading data. LAST_MODIFIED (option D) is not a valid COPY INTO option. The community discussion strongly supports A with 92% consensus and upvoted explanations confirming it's the optimal choice for this scenario.

Author: LeetQuiz Editorial Team