Help the family historian caption the old photograph correctly by choosing the right phrase.

Uncle Arthur ________ claims to be an intergalactic time traveler.

The correct answer is , who always wears a tin foil hat,.

Because "Uncle Arthur" is a specific, named person, the relative clause gives us extra, non-essential information about him. This makes it a non-defining relative clause, which must be separated by commas.

We use "who" for people, and we cannot use "that" in non-defining relative clauses!