Acute toxicity refers to toxicity from

• A. One time exposure to a pesticide
• B. Many small exposures to a pesticide
• C. 50% mortality is observed
• D. A nerve poison is formed

Answer: (A)

Acute toxicity describes adverse effects that occur after a single, short-term exposure to a pesticide, with rapid onset of symptoms or death. The best match is a one-time exposure because it captures the pattern that defines acute toxicity: effects arise from a single event rather than from repeated exposure over time. In practice, acute toxicity is often quantified using LD50 or LC50 values, which indicate the dose or concentration that causes death in about 50% of test animals after a single exposure. The other ideas don’t fit this pattern: many small exposures describe chronic or cumulative toxicity; a 50% mortality figure is a measurement used to assess acute toxicity but isn’t the definition itself; and forming a nerve poison relates to the substance’s action, not how the exposure is classified.