Studies show that repeated exposure to an allergen can trigger anaphyl

Sure Deepthis!

The questions asks us to mimic the reasoning of the argument. How does the author present his argument?

Repeated exposure to an allergen can trigger anaphylaxis (can be life threatening).
Then even minimal exposure can be life threatening.
(Repeated exposure reduces the resistance of the person against the allergen. Finally even minimal exposure of the allergen can be life threatening)

B. Because minor earthquakes can weaken the existing infrastructure in an area, a series of minor earthquakes sometimes causes much more extensive damage than might otherwise be expected.

Minor earthquakes weaken the infra so series of minor earthquakes keep weakening the infra more and more. Finally, even that small earthquake in the series can cause much more damage than you would expect. Just like minimal exposure can also be life threatening after repeated exposure to allergen.

C. Peanut allergy sufferers do not need to ingest peanut products in order to experience an allergic episode; a reaction can also be triggered by touching peanuts or peanut oils.

Minimal exposure to peanuts can produce an allergic reaction. But here, 'repeated exposure to something before' is missing.. As far as the argument goes, we don't know whether peanut allergy sufferers develop this condition by repeated exposure to peanuts or even without much exposure. In fact, the way it is worded, I would like to believe that it doesn't matter how much they get exposed to peanuts beforehand.. if someone has an allergy to peanuts, it will be triggered by even the tiniest exposure...