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': 'Most common pigment used in composite restorations are: \nSelect and explain. \nA. Oxides of iron, B. Oxides of chromium, C. Oxides of aluminium, D. Oxides of barium', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Inorganic oxides are usually added in small amounts to provide shades that match the majority of\xa0tooth shades. The most common pigments are oxides of iron. Numerous shades are supplied, ranging\xa0from very light shades to yellow to gray. Various color scales are used to characterize the shades of the\xa0composites. A UV absorber may be added to minimize color changes caused by oxidation. Darker and\xa0more opaque shades of composites cannot be cured to the same depth as the lighter translucent\xa0shades.', 'role': 'assistant'}]