What are the keywords in the following sentence? variety of fish on the market
fish, market, variety

What are the keywords in the following sentence? A clock and various arrival and departure times at a station.
arrival, clock, time

What are the keywords in the following sentence? letter b in eco style with a branch and leaves .
branch, leave, style

What are the keywords in the following sentence? the head of author embedded in an ancient tree
embed, head, tree