To analyze the expression \(2.5x + 10\):
- The term \(10\) represents the entry fee for the car.
- The term \(2.5x\) represents the total individual entry fees for \(x\) people, where \(2.5\) is the individual entry fee per person.
From this breakdown, we can see that the entry fee for the car is \(10\).
Therefore, the correct answer is: B) The entry fee for the car was $10.00.