What are the keywords in the following sentence? aircraft model remotely piloted aircraft in flight .
aircraft, flight, model

What are the keywords in the following sentence? an extreme example of a large tree totally engulfing a stone chamber with its roots .
engulf, root, tree

What are the keywords in the following sentence? earth and moon speaking with each other in space
earth, moon, space

What are the keywords in the following sentence? A ski teacher and his students pose for a photo together.
photo, pose, student, teacher