Answer:
The number of cars passing a tollbooth in a given hour.
Explanation:
Discrete variable is a variable that possess a countable number of values, means the value is obtained by counting.
1. the average annual increase in fuel price - This is not discrete as the values can be decimal. And it is obtained by measuring, so it is continuous variable.
2. a car's speed at different times - This is also not discrete. This is also continuous variable.
3. a person's weight - This is also not discrete.
4. the number of cars passing a tollbooth in a given hour - This is discrete as we can count the number of cars.