Ans. is 'a' i.e., Mercury Acrodynia or pink disease:* It is thought to be an idiosyncratic hypersensitivity reaction particularly seen in children. This can be caused by chronic mercury exposure in any form usually in children.* The onset is insidious with anorexia, insomnia, sweating, skin rash and photophobia.* Hands and feet become puffy, pinkish, painful, paraesthetic with peeling of skin.* Teeth may be shed.* Metallic mercury (para or quick silver) is not poisonous on ingestion, as it is not absorbed. But its vapours are poisonous. Mercuric compounds being soluble are more poisonous than mercurous compounds. Mercuric chloride (HgCl2), also called corrosive sublimate or perchloride of mercury, is most poisons salt of mercury.* Acute poisoning presents with syncope, convulsions general instability and nephrotoxicity (proximal tubular). The mouth, tongue and fauces become corroded and appears grayish white.* Signs and symptoms of chronic mercury poisoning are :1) Excessive salivation, metallic taste, loosening of teeth, and blue black lining on gums (similar to lead poisoning).2) Diphtheria like membranous colitis and dysentery.3) Anorexia, insomnia, sweating, nause, irritability and photophobia.4) Special features are :i) Mercuria lentis: Brownish deposition of mercury on anterior lens capsule.ii) Tremors : There are moderately coarse, intentional tremors starting in fingers and hands, and legs. They are also called Danbury tremors or hatter's shake or glass blower's shake. In severe form, patient becomes unable to dress, write or walk, i.e. concussio mercuralis (shaking palsy).iii) Erethism (neuropsychiatric changes): The personality disturbance is characterized by shyness, irritability, tremors, loss of memory and insomnia. There may be depression, delusion, hallucination and MDP (mad hatter).iv) Acrodynia (Pink desease): This is idiosyncratic hypersensitivity reaction with a generalized pinkish rash described as 5P : pinkish, puffy, painful, paraesthetic hands and peeling of skin.v) Minimata disease: It is due to organic mercury poisoning due to eating fish poisoned by mercury.vi) Membranous glomerulopathy.