Fill in the blank with the most appropriate word: The policeman _ that man if he doesn’t stop disturbing neighbours.

This question tests your understanding of verb tenses in conditional sentences. The sentence "The policeman _ that man if he doesn't stop disturbing neighbours." describes a future action that depends on a present condition.

In the First Conditional, the if-clause is written in the simple present tense, while the main clause takes the simple future tense using "will + base verb". Since the condition is "if he doesn't stop disturbing neighbours", the correct verb in the main clause is "will arrest".

• If-Clause: If he doesn't stop disturbing neighbours.
• Main Clause: The policeman will arrest that man.
• Rule: First Conditional = If + Present Simple, Will + Base Verb.

Therefore, the correct answer is: "Will arrest".