During the Gilded age the economy was growing very fast, but Industrialization brought high corruption levels, urban poverty and over-consumption of many items due capitalism was booming.
The railroads controlled all the prices, and farmers needed to rely on the railroads to transport their crops around the country; there was an increase in the number of farmers so their prices declined, and they were earning less and less; so many farmers lost their land not being able to compete, turning into tenant farming (<em>renting the right to farm</em>) they were farmers without farms. They were not able to keep up with inflation rates either.
I'd go with b.) high taxes on wealthy.
Abolition of the slave trade
