Question

find the appositive. if it is nonrestrictive, set it off with commas. if it is restrictive, submit the text without making any changes.
aboard the double-decker bus, a tour guide rhapsodized about londons storied history. his lecture an enthralling and unscripted monologue made passengers feel as though they were traveling through time.

Explanation:

The phrase "an enthralling and unscripted monologue" is a nonrestrictive appositive that adds extra, non-essential descriptive information about "His lecture." Nonrestrictive appositives require commas to set them apart from the main clause.

Answer:

Aboard the double-decker bus, a tour guide rhapsodized about London's storied history. His lecture, an enthralling and unscripted monologue, made passengers feel as though they were traveling through time.