Select the most appropriate option to fill in the blank.

I am your true friend, ______?

aren’t I

The phrase "aren't I" is the correct choice to fill in the blank. This phrase is a tag question that seeks confirmation or agreement from the listener. In this context, the speaker is affirming their role as a true friend and is seeking agreement or confirmation from the listener. The tag question "aren't I" is commonly used in English to confirm statements and is the grammatically correct choice in this sentence structure.