Logical reasoning PrepTest 153 · Section 2 · Question 4

Incorrect. Possibly true, but when negated all we get is " . . . is likely to want to own a dog," which doesn't change the validity of the argument in the stimulus at all.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Strengthen with Necessary Premise

Stimulus Summary:
The stimulus tries to convince us that large dogs are less troublesome than small ones for apartment dwellers with limited time to exercise a dog, because most large dogs need less intensive exercise than small dogs to stay fit. Dogs that don't get enough exercise are more troublesome than those that do.

Strategy Overview:
As always with NA questions, start by identifying the conclusion and paying attention to how it's supported—as well as what's missing from its support. Then, go through the answer choices and negate anything that looks promising. The negated answer that destroys the argument is your necessary assumption.

Answer Anticipation:
One thing that comes to mind here is the broad term "troublesome." Are there reasons other than limited exercise that dogs become troublesome? Could some of those be worse with a large dog? It's also worth noting that the stimulus didn't tell us much about how to exercise either large or small dogs "intensively." Is there something about intensive exercise, specifically, that is harder for apartment dwellers with limited time to provide for a dog? If fetching a tennis ball for 10 minutes counts as "intensive," most apartment dwellers could manage that, right?

Answer Explanation:
When negated, we get "does not require more time," which blows the argument in the stimulus out of the water. If intensive exercise and less-intensive exercise take the same amount of time, why would someone with limited time have to choose the dog that requires less-intensive exercise? That makes this the correct answer.

Key Takeaway:
Negate, negate, negate. Yes, we've told you this before, and yes, we're going to keep telling you. You will be cruising at close to 100% on Strengthen with Necessary Premise questions if you fully understand negation and use it every time.

Incorrect. If you picked this, you're probably a dog owner. Like many trap answers, easy to agree with if we're talking about the real world, but irrelevant on the LSAT. "Shoulds" and other moral judgements are rarely useful as necessary assumptions.

Incorrect. We can't all live in the Friends apartment, okay, LSAT?! More to the point, if you negate this you just get a rule about happier dogs in small apartments—nothing that affects the argument.

Incorrect. We don't know if staying fit is actually related to the troublesome behaviors of dogs at all, as opposed to some other benefit of exercise, so this isn't relevant; it also doesn't have anything to do with how much time it takes to care for a dog.