I chose C. Is C contradicted by the following from the passage: mold is almost always found in places where there is substantial moisture - because of "ALMOST always."?

This is an assumption question.

An unstated gap between the argument and its conclusion.

Regards

The conclusion of this argument is
To avoid mold poisoning --> identify moisture areas like plumbing leakage --> prevent leakage and prevent mold from breeding.

We can try negating the options..

A. Mold itself does not create moisture.
Suppose Mold creates its own moisture. Then identifying moisture areas is a futile exercise as mold would have formed already. Therefore we cannot prevent breeding of mold and hence the chain of reasoning in the conclusion become invalid.

B. Most homeowners know enough about plumbing to determine whether theirs is in good condition.
Suppose most homeowners do not know enough about plumbing. So what? Irrespective of their plumbing skills they can identify leakage and prevent breeding of mold. Does not change the conclusion.

C. Mold cannot grow in dry areas.
Suppose mold can grow in dry areas. So mold can grow in presence of moisture as well as dry areas. So prevent plumbing leakages to prevent breeding of mold in moisture areas. Tackle the mold in dry areas separately. It still does not change the conclusion on moisture-breeding mold.

D. No varieties of mold are harmless.
Suppose few varieties of mold are harmless. So there are still harmful mold that breed near moisture and hence the conclusion holds.

E. Mold spores cannot be filtered from the air.
Suppose mold spores can be filtered from air. Still the conclusion on preventing the breeding of mold near moisture holds true.

The BEST FIT is A.
One way of handling this kind of questions is to negate the options relating to the conclusion and see if the conclusion still holds true.

The best way to answer such questions is separate conclusion and argument of passage. Conclusion is that homeowners should maintain internal plumbing to avoid mold. Argument/evidence is that mold grows in moist areas.

This will eliminate B, since B is related to conclusion and not to argument. If the question was what assumption does the conclusion depend on, then it will be this answer (I think).

As for D and E, they aren't really about the argument. It is about the concept/topic that mold causes airborne illness.

For A and C, this can be tricky, I was stuck too for a couple of minutes. But again, C can be eliminated because argument is about mold and moisture. It says mold is almost always found in damp areas. The argument says that look for moisture areas as mold grows there, ignoring that moisture can be produced by mold.

I hope this helps.

The argument states that to avoid molds one should keep the plumbing in good condition. Therefore the assumption is that, mold does not create moisture. If mold created moisture then there no need to ensure plumbing be kept in good condition.

one crazy question,all option look correct!!