Was introduced in 1828 and consists of campaign slogans, rallies, buttons, and more recently television advertisements that denounce their rival candidates.

Smear campaigns , is the right answer.

Explanation:

The presidential election of the year 1828 in the United States was one of the most quarrelsome elections in the history of the United States. In this election, smear campaigns were introduced in the United States. The smear campaigns were consists of rallies, campaigning slogans, buttons, television advertisements that denounced the opposition and their candidates. These smear campaigns were introduced by Andrew Jackson, who was infuriated with the backdoor politics.

on april 6, 1917, the u.s. joined its allies--britain, france, and russia--to fight in world war i. under the command of major general john j. pershing, more than 2 million u.s. soldiers fought on battlefields in france.

the answer would more than likely a.)falling crop prices  

hope the answer is right and ,either way have a nice day.