What does curb weight include?

Curb weight is an important specification in understanding a vehicle's overall mass when it is not carrying passengers or cargo. Specifically, curb weight refers to the total weight of a vehicle with all of its essential fluids — such as oil, coolant, and a full tank of fuel — along with standard equipment, including the spare tire and tools that come installed from the manufacturer. This measurement gives a realistic idea of how heavy the vehicle is in a functional state, ready to operate, without additional load.

The other options do not fully capture the definition of curb weight. The weight of just the vehicle, without fluids or spare tires, would be too simplistic and not reflect the operational state of the vehicle. Similarly, including passengers or cargo would misinterpret curb weight, as it specifically measures the vehicle's weight alone in its standard condition. Lastly, only measuring the weight of cargo and the trailer tongue overlooks the vehicle's own mass entirely, which is crucial for understanding performance capabilities, fuel efficiency, and handling. Thus, option C accurately encompasses all necessary components of curb weight.