Bar•ren adj ˈber-ən, ˈba-rən
1: not reproducing: as a : incapable of producing offspring —used especially of females or matings b : not yet or not recently pregnant: habitually failing to fruit
2: not productive: as a : producing little or no vegetation : desolate b : producing inferior crops c : unproductive of results or gain : fruitless

"barren." merriam-webster. com. merriam-webster, 2012.
web. 6 may 2012.

according to the dictionary entry, what part of speech is the word 'barren'?
a) adjective
b) adverb
c) noun
d) verb
it's a.