I'm not going to __ in the argument between my two friends.

• A. take sides
• B. choose a side
• C. take on
• D. join in

Answer: (A)

Staying neutral in a dispute is expressed with the phrase take sides. When you say you’re not going to take sides in the argument between my two friends, you mean you won’t align with either person or support one over the other. That’s exactly how this idiom is used—to indicate choosing a position in a conflict.

The other options don’t fit as well. Choosing a side is understandable, but the usual, natural expression for neutrality is take sides. Take on would mean to accept a challenge or responsibility, which isn’t about participation in the argument. Join in would mean to participate in the argument, which contradicts the idea of not participating.