The word which best completes the sentence is haven't ? Hence the complete answer is: "The choir has participated in America's Got Talent, haven't they?
What is a Tag Question?
A tag question is a question that is derived from a statement and usually involves a pronoun.
A tag question is usually required to gain clarification or to highlight the meaning of something.
An example of a tag question is:
He deserves a second chance, doesn't he?
See the link below for more about Tag Questions:
https://brainly.com/question/24326668
