Which of frédéric chopin's compositions were known as "studies" which addressed particular technical challenges on the piano?

Chopin's composition that addressed the above were called 'etudes'. An etude is a French word for a specific type of piano composition, which means 'study'. An etude is part of a learning strategy to become a better pianist. The etudes are compiled of very difficult material and are usually short pieces. They are meant to be practiced.

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What is the following ?