This sentence technically doesn't contain an error in verb-noun agreement, however the noun "each one" is odd here. It should be "everyone"
The name given to the loose organization of people dedicated to helping escaped slaves get to free territory was the "Under Ground Railroad." Hope this answer helped!
Well, the only one that actually makes sense to me is C.
Because the amount of money in the world will change over time, the Constitution is never changing but the Congress changes every so often and knows what amount is appropriate for that time period. if that doesn't make sense I'm sorry it's a bit difficult to explain.