This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Microbiology
Frequent blushing ("erethism") is associated with poisoning of 
Select and explain. 
A. Mercury, B. Lead, C. Phenolic acid, D. Carbolic acid
A: Mercury
Answer: A: Mercury 
Explanation: Mechanism of toxicity:Mercury reacts with sulfhydryl (SH) groups, resulting in enzyme inhibition and pathologic alteration of cellular membranes.Clinical presentation:Severe chemical pneumonitis and noncardiogenic pulmonary edema.Acute gingivostomatitis may also occur.Chronic intoxication:Classic triad Tremor Gingivostomatitis. Metallic tasteFrequent blushing ("erethism")Pain in the extremities, often accompanied by pinkish discoloration and desquamation ("pink disease")