Which of the following protests was directly related to federal policies, and thus had the greatest impact in creating a negative public perception of the hoover presidency?
the farm holiday association
the ford motor company labor strikes
the bonus expeditionary force
the widespread appearance of “hooverville” shantytowns

  The Bonus Expeditionary Force.

Explanation:

 They were a group of 43,000 marchers, some of them veterans of World War I who gathered in Washington D.C. in 1932 to demand the payment of their service certificates.

  The name was given by the organizers as a reference to the American Expeditionary Forces. The media called them Bonus Marchers. The manifestation was supposed to be in peace, but when the Washington police attempt to remove the veterans after being ordered to do that by the Attorney General they resist. That lead to Hoover´s decision of sending the army to clear the marchers' campsite. It was considered politically disastrous to Hoover and was a contributing factor to the victory of Roosevelt in the 1932 election.

  I hope this answer helps you.