Problem: What are the most important words?
small flame in fireplace in the dark
Answer: dark, fireplace, flame

Problem: What are the most important words?
chromosome numbers of various organisms each species has a characteristic number of chromosomes in each cell .
Answer: chromosome, number, organism

Problem: What are the most important words?
steel framed building at a construction site ready for cladding with columns .
Answer:
building, column, frame