Answer:
Their slogan would have been:
A) Defend farmers and workers! Regulate business and industry
Explanation:
The Populist Party was a agrarian base political party, which aimed at improving conditions for the country's farmers and agrarian workers.
In the late 19th century, the farmers and agrarian workers started to get together to initiate a movement for their interests and against the interests of the elite. In 1876, Farmer's Alliance was established, aiming to put an end to a system which had thrown a lot of farmers below poverty line.
The Farmer's Alliance gathered a lot of farmers under its banner, but however, it proved politically ineffective on the national scale. To get into politicals and defend the interests of farmers and agrarians, the leaders of Farmer's Alliance formed Populust Party, and Farmer's Alliance died down.