Which of the following describes the effect of ozone at ground level?

Ground-level ozone is a significant air pollutant that poses various health risks to humans. Unlike ozone found in the stratosphere, which plays a protective role by blocking harmful ultraviolet radiation, ground-level ozone results from chemical reactions between volatile organic compounds (VOCs) and nitrogen oxides in the presence of sunlight. When inhaled, ground-level ozone can cause respiratory problems, exacerbate asthma, and reduce lung function. Therefore, option B accurately captures the harmful effects of ground-level ozone on human health.

The other options, while describing different aspects related to ozone and air quality, do not align with the realities of ground-level ozone's effects. For instance, ozone does not serve as a protective layer at ground level, and it does not enhance plant growth; rather, it can negatively impact plant health by damaging leaves and inhibiting growth. Additionally, while ozone can play a role in purifying the air by oxidizing certain pollutants, the overall impact of ground-level ozone is detrimental to both health and the environment. Thus, option B is the most accurate selection regarding the effects of ground-level ozone.