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Logical Reasoning · Weaken

PrepTest 154 · Section 2 · Question 5

Phase 1 (your first ~400 questions): read the guidance, then answer. No clock.

Step 1 · Pre-Question Guidance · read this first

Question type
Weaken
The one idea it tests
The cure secretly harms the very thing it claims to protect.
The basic logic
The argument says choosing a substitute reduces pressure on a threatened thing, so it will recover. Pop it by showing the substitute itself damages the threatened thing in another way the arguer ignored (Ignored Side Effect).
Tiny words that decide it
  • “as”
  • “leads to”
  • “thus”
  • “best reason”

Playground logic

Marcus says playing indoor video soccer instead of real soccer saves the grass field, since fewer feet trample it. Priya pops the burger: the new game room takes the field's sprinkler water. The substitute hurts the field in a sneaky new way.

Step 2 · The kid story

Saving the Grass, Supposedly

The school field is mostly dirt. Marcus has a plan. "Everyone should play video soccer in the new game room! It never rains in there, the controllers always work, and it's free. Best of all, fewer kids on the field means less trampling, so the grass will grow back thick." Frankie and Sharon start debating whether video soccer counts as exercise. Priya sips her juice box and reads the principal's newsletter. "Detective, the game room's cooling system runs on water pulled from the field's sprinkler line. The more the game room runs, the less water reaches the grass." Marcus stares. "So my rescue plan is drying out the field?" Lulu writes: Side effect, ignored. Biscuit digs another hole in the dirt, which does not help either.

Step 3 · Try the model question

Marcus: Video soccer in the game room beats field soccer because it is free, works in any weather, and the controllers never break. But the strongest reason is the grass: as more kids choose video soccer, fewer kids trample the field, so the grass can grow back and spread.

Which fact, if true, does the most damage to Marcus's argument?

Choices

Step 4 · The courtroom tale

The Paper Straw Defense

A cafe owner, Ms. Fennel, is sued by a neighbor over a dying oak tree. "Your Honor," she says, "I switched to selling plastic-free bamboo cups. Fewer customers buy paper cups, fewer paper mills cut oaks, so oaks everywhere will flourish." Mr. Whitfield rises, suspenders gleaming. "Charming. But the bamboo cups are rinsed with a cleaning solution that drains straight into the soil under that oak." He holds up a soil report. "Your client's substitute is poisoning the very tree she claims to protect." The judge peers at the report. "The plan lowers one harm and adds another, aimed right at the roots." Ms. Fennel looks at the oak and quietly orders a new drain pipe.

Step 5 · Work the real question

Open PrepTest 154, Section 2, Question 5 in your official copy from LSAC (for example in LawHub) and read it there.

Your answer

How to apply it

Find the top bun (the substitute helps the threatened thing) and the patty (less demand for the threatened thing means it recovers). Ask: could producing or using the substitute hurt the threatened thing some other way? The best weakener shows a side effect that cancels the claimed benefit. Skip choices about quality, taste, price, or human health that never touch whether the threatened thing actually recovers.