What are the keywords in the following sentence? lichen on the trunk of a tree
lichen, tree, trunk

What are the keywords in the following sentence? profession preparing to retrieve his net on a beach
beach, net, retrieve

What are the keywords in the following sentence? Several people walk by a rickshaw containing a sleeping cat.
cat, rickshaw, sleep

What are the keywords in the following sentence? the mountains surrounding in fall color
color, mountain, surround