Answer! how did roosevelt propose to prevent a return to the kind of stock speculation that he believed had cause the great depression?

His plan, called the New Deal, had greatly helped bring back the US to prosperity

Many programs like the CCC and WPA provided jobs to American swho became broke from speculation.

The SSA provided welfare to those who were disabled or elderly and couldn't function for themselves 

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https://www.thoughtco.com/top-new-deal-programs-104687