OFFICIAL EXPLANATION
Low-fat milk contains 50% fewer calories than does whole milk. Thus, a glass of low-fat milk is healthier than a glass of whole milk.
The above argument relies on which of the following assumptions?A. Skim milk contains fewer calories than does low-fat milk and is thus healthier.
Incorrect.
Skim milk is outside the scope of this argument, which only compares low-fat and whole milk. The assumption does not introduce any new factors (in this case, skim milk), but rather links existing factors.
In addition, this answer choice uses the word thus, which is a conclusion word. This means that the answer choice contains a conclusion. Since we're looking for an assumption and not for a conclusion, this answer choice can be eliminated.B. Low-fat milk is tastier than whole milk.
Taste is outside the scope of this argument. The assumption does not introduce any new factors (in this case, taste), but rather links existing factors.C. Whole milk is tastier than low-fat milk.
Taste is outside the scope of this argument. The assumption does not introduce any new factors (in this case, taste), but rather links existing factors to each other.D. Milk is healthy to lactose-tolerant people only.
Incorrect.
Lactose tolerance or intolerance is outside the scope of this argument. The assumption does not introduce any new factors (in this case, lactose tolerance), but rather links existing factors.E. The fewer calories a beverage contains, the healthier it is.
If the author assumed low-calorie drinks are healthier, that would explain why he or she concluded low-fat milk is healthier than whole milk, based on the premise that low-fat milk contains less calories.
Premise: that low-fat milk contains less calories than whole milk
Assumption: low-calorie drinks are healthier
Conclusion: low-fat milk is healthier than whole milk