What are the keywords in the following sentence? the spacecraft took this image of moon .
image, moon, take

What are the keywords in the following sentence? troops arrive at their barracks to reinforce fellow troops following the siege by militants
follow, militant, reinforce, siege, troop

What are the keywords in the following sentence? close up portrait of cheerful students with teacher at the classroom
classroom, close, portrait, teacher

What are the keywords in the following sentence? metabolism all chemical reactions occurring within an organism
metabolism, occur, organism, reaction