Final answer:
The appropriate SI base unit for the mass of an automobile is the kilogram (kg). It is used to measure the amount of matter in an object, and for larger masses such as vehicles, it is often expressed in kilograms or metric tons.
Step-by-step explanation:
The appropriate SI (International System of Units) base unit for measuring the mass of an automobile is the kilogram (kg). This is the base unit for mass in the SI system. It is important to note that mass is a scalar quantity that refers to the amount of matter in an object. In this case, we are referring to the amount of matter in an automobile. When we want to express very large masses such as the mass of an automobile, we usually express it in terms of kilograms or metric tons (1 metric ton equals 1000 kg).
Learn more about SI Units