What are the keywords in the following sentence? water rushes through the gorge below waterfall
gorge, rush, water

What are the keywords in the following sentence? sign of danger for rock falls in the cliffs in a beach
cliff, danger, fall, sign

What are the keywords in the following sentence? image titled buy a game from the step
game, image, step, title

What are the keywords in the following sentence? A pier has many boats parked in it.
boat, park, pier