

what I thought:
The gap I originally identified was "reducing stress can reduced the susceptibility to illness", since it was given that the scent of lavender reduce stress, and with this, I can get the scent of lavender reduce the susceptibility to illness. I knew I was wrong bc the scent of lavender can still reduce the susceptibility to illness for other reasons. (Am I correct on the analysis?)
The gap seems to be about the "intense stress", if people who regularly inhale the scent of lavender weren't under intense stress, it's unknown whether they'll be more susceptible to illness, and if they (people who regularly inhale the scent of lavender) weren't more susceptible to illness in the first place, the incidence of them (people who regularly inhale the scent of lavender) wouldn't be able to be reduced by inhaling the scent of lavender. (Am I correct on this?)
Any suggestions on tackling this kind of questions? Like how can I get closer to guessing what the intended gap is?