What are the keywords in the following sentence? A man serving hot dogs on a tray.
dog, serve, tray

What are the keywords in the following sentence? A white train hauling cargo along a track.
haul, track, train

What are the keywords in the following sentence? little sister learning how to count on abacus with the help of her older brother
abacus, help, learn

What are the keywords in the following sentence? Two zebras off to the side of an enclosure at a zoo.
enclosure, side, zoo