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 is false with regard to prevalence ? \nSelect and explain. \nA. It is a product of incidence and duration., B. It can be determined by a cross-sectional studies., C. It is a rate., D. Prevalence is point prevalence unless otherwise specified.', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Prevalence:\n\nPrevalence is defined\xa0as\xa0 "the total number of all individuals\xa0 who\xa0 have an attribute or disease at a\xa0 particular time\xa0 (or\xa0 during\xa0 a particular\xa0 period)\xa0 divided\xa0 by\xa0 the population at risk\xa0 of having the attribute or disease at this point in time or midway through the\xa0 period.\xa0\nAlthough referred to as a rate, prevalence rate is really a ratio.\xa0\nPrevalence is of two types :\xa0\n\n\xa0 \xa0 \xa0 \xa0 (a) Point prevalence\xa0\n\xa0 \xa0 \xa0 \xa0 (b)\xa0Period prevalence\xa0\n\nWhen\xa0 the\xa0 term\xa0 "prevalence\xa0 rate"\xa0 is\xa0 used,\xa0 without any\xa0 further\xa0 qualification,\xa0 it\xa0 is\xa0 taken\xa0 to\xa0 mean\xa0 "point prevalence".', 'role': 'assistant'}]