By nature, unpolluted rainfall:

Unpolluted rainfall is characterized by a pH that typically falls between 5.0 and 5.6. This mild acidity is a result of the natural presence of carbon dioxide in the atmosphere, which dissolves in rainwater to form carbonic acid. While rainfall is often associated with neutrality (a pH of 7), the presence of natural acids ensures that the pH is slightly below neutral.

In contrast to this, options that suggest that unpolluted rainfall is devoid of particulate matter or is slightly alkaline are less accurate. While it is true that clean rain may have fewer particles than polluted rain, it is not completely devoid of particulate matter; natural aerosols can still be present. The notion of falling only in high lakes areas does not accurately reflect the global distribution of rainfall. Rainfall occurs in a variety of geographic settings, not limited to specific regions. Thus, the characteristic pH range for unpolluted rainfall stands out as the defining feature of its chemical nature.