What are the keywords in the following sentence? entrance with soldiers standing guard
entrance, guard, stand

What are the keywords in the following sentence? pilot boat navigating towards cargo ship
boat, navigate, ship

What are the keywords in the following sentence? a herd of cows grazing grass .
cow, grass, graze, herd

What are the keywords in the following sentence? A butterfly has lit on the head of this sleeping toddler.
butterfly, sleep, toddler