Question

A function, f(x), represents the distance, in miles, that Sarah drives each hour, x.

Answer 1

In this situation $x$ will represent the time in hours. Since time cannot be negativ, we can rule out the second and the third answers. Also, Sarah in certain situations will drive for half an hour or more than one hour, like 0.5 hours or 1.3 hours. Since you can represent those numbers with integers, we can also rule out the second answer. So the only option left, is the fourth one.

We can conclude that the domain of the  function, f(x), that represents the distance, in miles, that Sarah drives each hour is the set of all real numbers greater than or equal to zero.