Some people who regularly inhale the scent of lavender would otherwise be under enough stress to
Why this is right
The argument is trying to make use of this causal chain: Inhale ? stress ? immune system ? less lavender reduced less impaired illness The first sentence well establishes that first arrow. But the second arrow isn't accurate. We only know that intense stress can impair the immune system. The first sentence ends with "reduced stress" and the second one begins with "intense stress", so it feels like the 2nd sentence is picking up whether the 1st one left off, but there's a gap there (most of us don't notice it when we read the argument, so we didn't want to disingenuously include it in our Evaluate write-up). If the people who regularly huff lavender are chilled out hippies who have low or even normal stress levels, then even if they stopped smelling lavender, they still wouldn't have the sort of intense stress that messes up your immune system. Thus the stress reduction afforded by the lavender isn't actually saving their immune system from any dysfunction. If we negate this answer, the "some" (at least one) turns to "none" (zero): None of the people who regularly inhale lavender would otherwise (if they stopped inhaling lavender) be under enough stress to impair their immune system. This would badly crush the argument. Another fun fact --- if we noticed the New Term in the conclusion, "those who regularly inhale the scent of lavender", we could have thought, "The argument didn't tell me anything about that group of people, so the author must be assuming something about them". (B) is the only answer that addresses people who regularly inhale lavender.
Skill tested: Necessary Assumption · how this choice captures the argument's function is the move to repeat next time.