This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Dental
[{'content': 'Main drawback of Be in Ni-Cr alloys \nSelect and explain. \nA. Health hazard, B. Increase flow of alloy, C. Reduce fusion temp, D. Refine grain bending', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Although beryllium is known to be highly toxic, it is used in some Ni-Cr alloys in concentrations of 1% to 2% by weight (approximately 5.5% to 11% atomic content) to increase the castability of these alloys and lower their melting range. It also tends to form thin adherent oxides that are required to promote atomic bonding of porcelain.\xa0\nBase metal alloys containing both beryllium and nickel exhibit high beryllium release rates, which may pose a health risk.\nBeryllium-containing particles that are inhaled and reach the alveoli of the lungs may cause a chronic inflammatory condition called berylliosis.\xa0\nBerylliosis occurs only in individuals with a hypersensitivity to beryllium and may occur from inhalation of beryllium dusts (from grinding or polishing alloys), salts, or fumes such as those encountered in casting beryllium-containing alloys. Thus, dental lab technicians would presumably be at the highest risk of adverse effects from exposure to beryllium dusts and vapors.\nRef: Phillip’s 12th edition page 128.', 'role': 'assistant'}]