Which of the following statements about heavy metals is true? A. Their specific gravity exceeds that of water by five or more times. B. None of them is necessary to sustain life. C. All of them are toxic even at trace levels. D. All of the above. E. None of the above.

Their specific gravity exceeds that of water by five or more times. (Ans. A)

Explanation:

Heavy metals are known as the element which can be two types one is present in the earth's shell and another is man-made sources. The chemical composition of heavy metals has a high density compared to water and low poisonous concentrations.

Some examples of these elements are lead, mercury, arsenic. Heavy metals consisting of elevated atomic weight with a certain gravity that helps to exceed the specific gravity of H2O by 5 or more times at 4°C temperature.

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