The domain of a function refers to the set of all possible inputs, or in this case, all possible times, t, that Tanya could be walking.
In this context, Tanya's walking time could be any duration from t=0 when she started walking all the way to t=17 when she ended her walk.
Since time is continuous, these times can take any value within that range. It is not constrained to just whole minutes, but can include fractions of minutes as well. For instance, Tanya could have been walking for 7.5 minutes, or 10.2 minutes, or any other real number between 0 and 17.
Therefore, the most appropriate type of numbers for the domain of the function d(t) are real numbers. The real numbers include all the possible times that Tanya could be walking, whether those are whole numbers or fractional numbers.
Therefore, the domain for this problem is the set of all real numbers from 0 to 17 inclusive