Question

Add a question tag They live in London, .........?
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Answer 1

Answer: THE ANSWER IS DON'T THEY

Step-by-step explanation:

Answer 2

A possible question tag for this sentence is:

They live in London, don't they?

This is because a question tag is an additional and very short question at the end of a regular sentence (such as "...don't you?" or "...isn't it?")