Which statement best describes how ground-level ozone forms and its health and crop effects?

• A. Ozone forms from NOx and VOCs in sunlight; it irritates airways, reduces lung function, and damages plants.
• B. Ozone is formed when rainwater dissolves ozone directly and has no effect on ecosystems.
• C. Ozone is formed only during night-time reactions; it improves crop growth.
• D. Ozone is the same as oxygen gas; no health effects.

Answer: (A)

Ground-level ozone forms when sunlight drives reactions between nitrogen oxides and volatile organic compounds released from vehicles, industry, solvents, and some natural sources. The presence of bright sun and warm temperatures in the air promotes these photochemical reactions, so ozone tends to accumulate on hot, sunny days with little wind.

When inhaled, ozone irritates the respiratory system, causing coughing, throat irritation, chest tightness, and reduced lung function. It can worsen asthma and other lung conditions, especially for children and people who spend a lot of time outdoors. For plants, ozone damages leaf tissues, reduces photosynthesis, and can lower crop yields and overall plant health.

A key distinction is that this ground-level ozone is different from the protective ozone layer high in the atmosphere, and it is not produced by rain dissolving ozone or by nighttime reactions. The description that ozone forms from NOx and VOCs in sunlight and that it harms both human health and crops captures the core idea and effects accurately.