Answer: Cadmium (Cd).
- A Mercury (Hg)
- B Lead (Pb)
- C Arsenic (As)
- D Cadmium (Cd)
Correct answer: D. Cadmium (Cd)
Explanation: Itai-itai disease occurred in Japan due to cadmium from zinc-smelting operations contaminating irrigation water. Cadmium replaces calcium in bones, causing softening, painful fractures, and renal failure. Do not confuse it with Minamata disease, which is caused by mercury.
Classical smog is a reducing mixture of SO₂ and fog, while photochemical smog is an oxidising mixture generated by UV-driven reactions of NOx and hydrocarbons.
Concept context
Understand how human activities alter the atmosphere, water, and soil. Covers air pollutants, smog types, ozone depletion, acid rain, greenhouse effect, water and soil pollution, and the principles of green chemistry.