What are the keywords in the following sentence? firefighters work to gain control of a fire on thursday .
fire, firefighter, thursday

What are the keywords in the following sentence? A large clock is at the top of a tower of a castle.
castle, top, tower

What are the keywords in the following sentence? A train station with various sets of tracks and two passenger trains on the tracks.
set, station, track, train

What are the keywords in the following sentence? image titled cite a website in text
cite, image, text, title, website