Option B is the best choice as in the line it requires up to four times more milk to make than conventional yogurt does, Greek yogurt produces larger amounts of acid whey, which is difficult to dispose of as in the production of yogurt large amount of gases are released as it creates acid which is difficult to dispose of for which farmers has found the use of this acid as it can be used livestock feed as a protein.
Scientists and govt are also working to re-use this acid. They are trying to use these conservation methods, costly but worthy
More in this passage the benefits of Greek Yogurt is explained by Nutritionists.
Hence, option B is satisfying.