PT56.S2.Q23 - Can anyone explain how this is an illegal reversal to me?

smcintosh0051-1

https://www.manhattanprep.com/lsat/forums/q23-ecologist-without-the-intervention-of-t579.html

The question is described here. It is PT 56 Section 2 Question 23. I was stuck between D and E and eventually chose D. I have read that it is incorrect because it is an illegal reversal, I just do not understand how.
I basically wrote it out like /Intervention -> Extinct and contraposed that as /Extinct -> Intervention which led me to answer choice D. What did I do wrong?

Admin Note: https://7sage.com/lsat_explanations/lsat-56-section-2-question-23/

luffyyyy

ok but what does D actually say? D says "If conservationists intervene to help squirrel monkeys survive, then the squirrel monkeys will not become extinct", which translates to "Intervene --> /Extinct". Is that the same as what you wrote ? You wrote /Intervention --> Extinct

JY Disciple

Just to share the way I approached this Q: I first had to decide if was going to use "extinct and not extinct" or "survive and not survive." I usually see like terms better if I commit to one synonym. So to make it easy on my brain, I used "survive and not survive."

Remember "Without" is negate sufficient; you will also see IF (sufficient) in this passage.
CP = Contrapositive

Sentence 1: /Intervention -->/Survive
Sentence 1 CP: Survive --> Intervention

Sentence 2: Forest Habitat Preserved -->Survive
Sentence 2 CP /Survive -->/Forest Habitat Preserved

Let's chain up the like terms:
Inference 1: /Intervention -->/Survive -->/Forest Habitat Preserved
Contrapositive: Forest Habitat Preserved --> Survive -->Intervention

Answer Choice E comes from the line marked Inference 1: /Intervention -->/Forest Habitat Preserved

Hope this helps.