Advertisement: Honey Oat Puffs cereal is made with whole-grain oats.
Evidence
Honey Oat Puffs cereal is made with whole-grain oats.
Health experts agree that whole-grain oats are far more healthful than most of the foods in a typical diet.
Conclusion (so)
Most people would have more healthful diets if they ate Honey Oat Puffs for breakfast.
Evaluate
This is one of those arguments that seems rather simple—so simple that the flaw can be easy to miss.
What if the LSAT only gave us the second premise and the conclusion:
Health experts agree that whole-grain oats are far more healthful than most foods in a typical diet.
Therefore, most people would have more healthful diets if they ate Honey Oat Puffs for breakfast.
There are a couple of potential problems with the argument, but ideally we would look at this and say,
Granted, the actual argument does state that Honey Oat Puffs are made with whole-grain oats. But this still only tells us that one ingredient in the cereal is healthful. It doesn't automatically mean that Honey Oat Puffs are healthful. What if they're loaded with sugar? What if they contain other ingredients that are known to be bad for our health?
The argument assumes that a characteristic of one ingredient applies to the cereal as a whole. That's one of the famous flaws, a Part vs. Whole flaw.
Goal
Look for an answer that describes a Part vs. Whole flaw. There are some other gaps in the argument, too, so we need to keep an open mind. We should give any answer that seems relevant a close look. Beware of answers that describe something which doesn't happen at all in the argument.
And we don't care if LSAC really knows what Honey Oat Puffs tasted like. They probably tasted like Tasty Wheat.