The question lists “Honey Fungus” as the correct answer. This is not necessarily true, and depends on several factors, including the definition of “largest”, and whether it includes clonal colonies. The question should probably be removed, though it could be retained if significantly narrowed in scope. (A more correct answer is probably Pando, a Quaking Aspen colony, but that’s only the most massive. The largest in area is a clonal colony of sea grass off Ibiza. All this is from Wikipedia, but the article does include references.)
I’ve chosen not to include links, so as not to trigger spam filtering.