All Labrador retrievers bark a great deal.
Conclusion (therefore)
Rosa’s dogs are moderate barkers.
Evidence
All Labrador retrievers bark a great deal.
All Saint Bernards bark infrequently.
Each of Rosa’s dogs is a cross between a Labrador retriever and a Saint Bernard.
Evaluate
The argument concludes that because one group (Rosa’s dogs) is a mix of two other groups (Labrador retrievers and Saint Bernards), the trait of barking will be a mix of how much each of the two groups is known to bark.
That might seem reasonable in some contexts. If I mix a spicy food with a mild food, I'll get something moderately spiced. If I mix some tequila with some sprite, I'll get something moderately alcoholic / moderately sweet.
But it doesn't work with genetics all the time. If Johnny is a mix of his mom and his dad's DNA, and she has blue eyes and he has brown eyes, that doesn't mean that Johnny will have bluish-brown eyes.
With genetics, sometimes a dominant gene beats a recessive gene and so the resulting trait matches one of the two inputs, not a mix of the two inputs.
Goal
Even if we don't understand why this argument structure is objectionable, we can head to the answers looking to copy it.
Thing 1 is a lot of X. Thing 2 is a small amount of X. Thus, a mix of Thing 1 and 2 will be a moderate amount of X.