Which of the following cosmic structures is the largest?
Galaxy
Galaxy filament
Galaxy cluster
Supercluster
Galaxy filaments are the largest known structures in the universe. They group galaxy superclusters, which in turn are formed by cluster composed of galaxies. Hercules–Corona Borealis Great Wall  is considered the largest known structure of Universe. It is estimated to span 10 billions light years. 
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Galaxy
Galaxy filament
Galaxy cluster
Supercluster
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