he highest nonzero dose at which no toxic effect is observed in a study on animals is called

Correct option is B

The No Observed Adverse Effect Level (NOAEL) is the highest dose of a substance at which no observable toxic effects occur in tested organisms, usually under laboratory conditions. This threshold is used to determine safe exposure levels for humans by incorporating safety margins.
Information Booster: NOAEL plays a significant role in toxicology, drug development, and regulatory science, where it guides permissible exposure limits in food, water, and air. It serves as the starting point for calculating Acceptable Daily Intakes (ADIs) or Reference Doses (RfDs).
Additional Knowledge:
· LD50: Refers to the dose lethal to 50% of test subjects.
· LOAEL (Lowest Observed Adverse Effect Level): The lowest dose at which adverse effects are observed.
· NOEFF: Incorrect term not used in toxicological studies.