Correct answer is (a) Nonfat Dry Milk
For explanation: Nonfat dry milk and skimmed milk powder are very similar but are defined by two different sets of regulations and authorities. Both contain 5% or less moisture (by weight) and 1.5% or less milkfat (by weight). The difference is that skimmed milk powder has a minimum milk protein content of 34%, whereas nonfat dry milk has no standardized protein level.