A public opinion poll in Ohio wants to determine whether registered voters in the state approve of a measure to ban smoking in all public areas. They select a simple random sample of 50 registered voters from each county in the state and ask whether they approve or disapprove of the measure. The proportion of registered voters in the state who approve of banning smoking in public areas is an example of:. A. a parameter. B. an unbiased statistic. C. a statistic. D. a sample proportion.