Read the passage and answer the question.
Astronomers from the University of Washington have used data from the
Kepler spacecraft to confirm that TRAPPIST-1h orbits its star every 19
days. At six million miles from its cool dwarf star, TRAPPIST-1h is located
beyond the outer edge of the habitable zone, and is likely too cold for life
as we know it.
Which word or phrase provides the best clue to the meaning of the
word habitable?