Base SI unit is the unit that used for simple quantity like time=second and length= meter. They only have one unit.
Derived unit is more complex because you multiply or divide at least two base SI, making it have more than 1 unit. The example could be velocity which was time/length = m/s
57 nuetrons and 44 elctrons just incase you need it there are 44 protons too.Hope this halps
The answer is A. Urinary system
