It gave them things to trade with other countries and themselves in order to establish kingdoms
they are kind a like laws if you think about it
Answer:
The answer should be: Companies replaced hand-operated brakes with air brakes on trains.
Explanation:
You have to think how hard it was for trains to stop with hand operated brakes. Trains go fast, and not stopping in time can be dangerous. Hope this helped :)
Not sure but I think it allowed states to pass laws segregating People based on race
