The function f(x) = 0.5x + 3 is used to estimate the number of pounds of potatoes a caterer plans to make depending on the number of people being served, x. The mathematical domain for the function is the set of real numbers.

The mathematical domain includes all real numbers, but the reasonable domain must reflect what x represents. Since x is the number of people being served, it must be a positive whole number; a fraction of a person or a negative number of people would not make sense. Therefore, the reasonable domain contains only positive whole numbers, choice B.

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