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': 'Retarder in zinc oxide eugenol is \nSelect and explain. \nA. CaCl2, B. Zinc acetate, C. Alcohol, D. Glycerine', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Setting Time and Factors Affecting\xa0ZOE:\nThe normal reactivity between zinc oxide and eugenol is very limited and must be accelerated in order for the material to have a practical clinical application. Acceleration of the set may be achieved by:\n\nIncorporating chemical accelerators in the mix (the most efficient and predictable way of controlling the setting time).\nReducing the powder particle size, providing for accelerated reactivity.\nIncreasing the powder: Liquid ratio (of limited effect in reducing the setting time).\nIncreasing the percentage of rosin and fillers.\nIncreasing the temperature and/or humidity.\nAdding water to the original mix or after mixing is complete and seated into the preparation.\nIntroducing greater energy in the mixing procedure (pressure-movement and time).\n\nA delay in setting is rarely needed. This is accomplished by adding vegetable oils or glycerin which keep the mass plasticized for a long period of time.\nRef: Marzouk’s operative dentistry page no 263', 'role': 'assistant'}]