The haymarket affair: group of answer choices was started by the knights of labor. was blamed on seven anarchist leaders despite a lack of evidence. took place in san francisco. led to passage of the foran act of 1885. marked the beginning of the federation of organized trades and labor unions.

The answer is:

was blamed on seven anarchist leaders despite a lack of evidence.

Explanation:

The Haymarket affair was a  violent confrontation between police and labor protesters in Chicago it occurred on May 4, 1886, it turned into a riot after someone threw a bomb at police. Eight radical labor activists were convicted in connection with the bombing. One of the condemned men killed himself in prison, and four others were hanged on November 11, 1887. Two of the men had their death sentences commuted to life in prison by the governor of Illinois.

The incident was viewed as a setback for the organized labor movement in America.

the united states didn't wanted to get involve with other countries probelms