Linked from
The 36 pages that link to SI base unit, each with the reason it gives.
SecondNarrower topic: The second is the base unit for the time dimension.
JouleNarrower topic: The joule is derived from the kilogram, metre, and second.
KilogramNarrower topic: The kilogram is the SI base unit assigned to mass.
MoleNarrower topic: The mole is one of the seven SI base units.
AmpereNarrower topic: The ampere is one of these units, defined independently of other SI units.
Amount of substanceNarrower topic: The mole is one of the SI base units.
Day (time unit)Narrower topic: The second, not the day, is the SI base unit for time.
X unitNarrower topic: Modern length measurements trace to the meter rather than a calcite standard.