Choose the option that best completes the sentence. When they started the fighting, the man who tried to ____ was knocked down.

To determine the best word to complete the sentence, we need to understand the meaning of each option and how it fits within the context of the sentence. The sentence is: "When they started the fighting, the man who tried to ____ was knocked down."

Intrude: This means to enter a place or situation where one is unwelcome or uninvited. It does not specifically relate to stopping a fight.

Interpose: This means to place or insert between one thing and another, which can imply a physical act of stepping between people. However, it can also simply mean to insert a comment or interrupt verbally.

Intervene: This means to come between disputing people or groups with the intention of stopping conflict. It is commonly used when someone steps in to stop a fight.

Obstruct: This means to block or hinder progress. It does not specifically involve stopping a fight between people but rather impeding movement or progress.

In the context of the sentence, the most appropriate word is "intervene". The sentence implies that the man attempted to stop the fight or dispute that started. Using "intervene" makes the sentence logical because the man is trying to stop the fighting and as a result, he was knocked down. "Intervene" is the word that best describes the action of stepping into a conflict to stop it.