Final answer:
The independent variable in the scenario where a zoo charges a fixed amount for parking and a variable amount per child is the number of children, as it determines the final cost of the tickets.
Step-by-step explanation:
To determine which variable is the independent variable in the context of a zoo charging $6 for parking and $17.50 for each child, we should identify the variable that is being manipulated or controlled in the scenario, which is typically the cause in a cause-and-effect relationship. In this case, the number of children would be the independent variable since the total cost is dependent on how many children are present. Parking is a constant charge and is not dependent on the number of children, making it a separate fee rather than a variable.
In a situation where the cost of tickets for children is in question, 'child' would be the correct option as the independent variable. Hence, the correct answer is Child (b). It's the factor that determines the final cost, aside from the flat parking fee.