Answer:
mass
Explanation:
because the unit kg is S.I unit of mass
#1 the relationship between universes and galaxies is that galaxies are made up of universe. and the relationship between stars and solar systems is every solar system contains at least one star.
#2. galaxies form after several planets form rather close to each other.
#3. the last one I don't know
The amount of stuff inside the cell and outside the cell are equal
