Answer: LD means lethal dose. LD50 is the amount of a material, administered at once to cause the death of half (50%) of a group of test organisms. A test which shows that LD50 of a certain chemical is 20 mg per kg means that 20 milligrams of that chemical for every 1 kilogram body weight of the test animal when administered in one dose, causes the death of 50% of the test group.
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