Final answer:
The correct unit used to measure mass is A) Kilogram (kg). The definition of a kilogram has evolved over time and is now based on fundamental physical constants for improved precision and stability.
Step-by-step explanation:
The unit used to measure mass is the kilogram (kg). A kilogram was originally defined by its relationship to the mass of 1 liter of water, but this definition has since evolved. It was most recently linked to a platinum-iridium cylinder standard. However, due to issues with long-term stability, in May 2019, the definition of a kilogram was updated to rely on fixed numerical values of several fundamental physical constants, such as the Planck constant, which ensures a more reliable and immutable standard.
Therefore, the correct answer to the question is A) Kilogram (kg), as degrees Celsius is a measure of temperature, and liter is a unit of volume, not mass.