For the Yelp business which had the most number of "long" reviews, which category does it belong to?
long reviews refers to review_length = 'long'; most number of long reviews refers to MAX(COUNT(review_length = 'long')); category refers to category_name;
SELECT T4.category_name FROM Reviews AS T1 INNER JOIN Business AS T2 ON T1.business_id = T2.business_id INNER JOIN Business_Categories AS T3 ON T2.business_id = T3.business_id INNER JOIN Categories AS T4 ON T3.category_id = T4.category_id WHERE T1.review_length LIKE 'Long' GROUP BY T2.business_id ORDER BY COUNT(T1.review_length) DESC LIMIT 1