Consider the following statements : 1. Other than those made by humans, nanoparticles do not exist in nature. 2. Nanoparticles of some metallic oxides are used in the manufacture of some cosmetics. 3. Nanoparticles of some commercial products which enter the environment are unsafe for humans. Which of the statements given above is/are correct ?

Says some elements are 'naturally occurring' while others are artificially made, establishing a category distinction between naturally present substances and human-made ones.

A student could combine this with knowledge that elements/compounds can form extremely small particles (e.g., dust, soot, mineral grains) to infer that naturally occurring very-small-scale particles might exist.

Explains atoms combine to form molecules and gives examples of naturally occurring elements and simple molecules, implying natural formation of small-scale particles from atoms.

Using basic chemistry and scale facts (atoms → molecules → clusters), a student could reason that natural processes could produce particulate clusters at nanometer scales.

Defines 'Nature' as life and non-life forms that exist independently of humans and treats materials from nature as resources when used, implying many materials exist without human manufacture.

Combine this with geological and biological knowledge (minerals, volcanic ash, biogenic particles) to suspect naturally formed tiny particles exist independent of humans.

Discusses microparticles (micron-sized plastic beads) being present in the environment and ingested by organisms, illustrating that small particles exist in ecosystems and are relevant at small scales.

A student could note that if micron-scale particles occur and affect organisms, then by analogy and known size ranges, even smaller (nano-scale) particles may also be present naturally (e.g., from biological or geological sources).

Provides a classification 'according to their existence in nature', distinguishing 'qualitative pollutants' that do not occur in nature, which implicitly acknowledges that some pollutants/particles do occur naturally.

Use this rule to reason that since the classification separates man-made from naturally occurring substances, there is a recognized category of naturally occurring particulate matter that could include nanoparticles.