Why was petroleum called “black gold”

Because when crude oil is extracted from the land it is a black color. people call it gold because of its oils and value it is very difficult to find so that’s why it’s call black gold

Ithink it’s a : ) good luck on whatever

They made a checks and balance system to equal power within the branches. the "check" meant that one branch would watch one branch and "balance" them if they were too powerful. if you want more info on this, i would just google checks and balance system.