Final answer:
The fundamental SI unit is the kilogram.
Step-by-step explanation:
The fundamental SI unit among the given options is the kilogram (c).
The kilogram is the base unit of mass in the International System of Units (SI). It is defined as the mass of the international prototype of the kilogram, a platinum-iridium alloy cylinder kept at the International Bureau of Weights and Measures (BIPM) in France.
The other options, such as kilometer (a), kilocalorie (b), and coulomb (d) are derived units in the SI system.
Learn more about SI unit