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': 'Which of the following represents the rheological behaviour of dilatant liquids? \nSelect and explain. \nA. A, B. B, C. C, D. D', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Newtonian viscosity:\xa0An “ideal” fluid produces shear stress proportional to the strain rate. That is, the greater the force applied, the faster the\xa0fluid flows and the plot is a straight line.\nPseudoplastic viscosity:\xa0The\xa0viscosity\xa0of\xa0many\xa0dental\xa0materials\xa0decreases\xa0with increasing strain rate until it reaches a nearly constant value.\xa0\nThat is, the faster they are stirred, forced through a syringe, or\xa0squeezed,\xa0the\xa0less\xa0viscous\xa0and\xa0more\xa0fluid\xa0they\xa0become.\nLiquids that show the opposite behavior are dilatant and become more rigid as the rate of deformation (shear strain rate) increases. That is, the faster they are stirred,\xa0the more viscous and resistant to flow they become.\nFinally, some classes of materials behave like a rigid body\xa0until some minimum value of shear stress is reached. This is\xa0represented\xa0by\xa0the\xa0offset\xa0along\xa0the\xa0shear-stress\xa0axis.\xa0These fluids, which exhibit rigid behaviour initially and then attain\xa0constant\xa0viscosity,\xa0are\xa0referred\xa0to\xa0as\xa0plastic.\nThe viscosity of most fluids decreases rapidly with increasing\xa0temperature.\xa0Viscosity\xa0may\xa0also\xa0depend\xa0on the previous\xa0deformation\xa0of\xa0the\xa0liquid.\xa0Such\xa0fluids\xa0become\xa0less\xa0viscous and\xa0more flowable\xa0upon\xa0repeated\xa0applications\xa0of\xa0pressure\xa0and\xa0are\xa0termed\xa0thixotropic.\nKey concept', 'role': 'assistant'}]