Explanation:
The high energy radiations, salts of heavy metals, CO and protein poisons like cyanides, make protein inactive by the sudden change in pH. Heavy metal toxicity has proven to be a major threat and there are several health risks associated with it. The toxic effects of these metals, even though they do not have any biological role, remain present in some or the other form harmful for the human body and its proper functioning. Hence, the correct option is (C).