Which brewery does the most purchased root beer in 2016 belong to?
most purchased root beer refers to MAX(COUNT(BrandID)); in 2016 refers to PurchaseDate > = '2016-01-01' AND PurchaseDate < = '2016-12-31';
SELECT T2.BreweryName FROM rootbeer AS T1 INNER JOIN rootbeerbrand AS T2 ON T1.BrandID = T2.BrandID WHERE T1.PurchaseDate BETWEEN '2016-01-01' AND '2016-12-31' GROUP BY T2.BrandID ORDER BY COUNT(T1.BrandID) DESC LIMIT 1