Checks and Balances are all spread through out the branches. Each one is designed so no one branch became to powerful, each branch has to check and balance another one.
D.
Because the author can show how characters change (A), but they need to show how the characters acted before the change (C). And B is just what explains the character.
I think its D, they would be able to ship livestock via railroad
The answer is a) Division of labor.
Hope this helps!
-Payshence xoxo