What are the keywords in the following sentence? free image of a rippling brook flows through in a forest .
brook, flow, forest

What are the keywords in the following sentence? grainy image of two trains on tracks moving through a city
city, image, track

What are the keywords in the following sentence? players leave the pitch after their match is abandoned
leave, match, pitch, player

What are the keywords in the following sentence? youths covered with coloured powder after celebrating holiday
celebrate, cover, holiday