The question requires selecting the correct phrasal verb to complete the sentence about reaching an agreement after negotiations.

Phrasal Verb Usage: Reaching Agreement

The phrasal verb 'arrive at' is used to mean successfully reach, achieve, or come to a decision, agreement, or conclusion.

• In the context of the sentence, "the two sides finally arrived at an agreement" means they successfully concluded the negotiations and reached a mutually acceptable deal.

Analysis of Options

Let's examine why 'arrive at' is the correct choice:

• Arrived at: This idiom specifically means to reach a conclusion or agreement. Example: "After much debate, we arrived at a compromise." This fits the sentence perfectly.
• Arrived to: This preposition is typically used when arriving at a destination or place, not an abstract concept like an agreement.
• Arrived on: This preposition is used for dates or surfaces, not for reaching agreements.
• Arrived with: This indicates accompaniment or bringing something, which is irrelevant here.

Therefore, the correct phrasal verb to indicate the successful conclusion of negotiations is 'arrived at'.