Answer:
a. The Haymarket protest turned vigorous when someone bombed a policed.
Step-by-step explanation:
The Haymarket protests had been instigated by the workers as labour protests for worker's rights. Following the riots and killing of people, a meeting called by labour leaders which included police, strikers and the Mayor of Chicago had been called. While the meeting had been deemed peaceful, things turned from bad to worse.
The attempt to neutralize the crowd after the meeting ended resulted with more riots when a random person threw bomb in the air. Police and civilians were killed and injured in the process.