Which of the following substances would an air scrubber most effectively filter?

An air scrubber is specifically designed to purify the air by removing harmful particles, pollutants, and allergens. When it comes to filtering substances from the air, dust and allergens are the primary targets of these devices. Air scrubbers typically utilize HEPA filters, which are highly effective at trapping small particles, including dust, pollen, pet dander, and various allergens, preventing them from recirculating back into the environment.

In contrast, liquid spills on the floor do not involve air filtration but rather require absorption and cleanup methods. Visible mold on surfaces also requires physical removal and possibly chemical treatments rather than air filtration, as air scrubbers are unable to filter out solid materials attached to surfaces. Strong scents from candles present a complex challenge because while air scrubbers can reduce particulates and some odors, they are generally less effective at neutralizing certain volatile compounds responsible for strong scents. Therefore, the effectiveness of the air scrubber is maximized in filtering dust and allergens in the air, making that the correct choice.