The answer is an adjective so it would be number 3
Since a participle takes the form: verb + -ing, the only word in this sentence which has such a form is B, 'challenging'. 'Puzzle' is a noun, 'crossword' is an adjective, 'created' is a verb.
Poor physical health can lead to an increase risk of developing mental health problems.
Wabash River and the Ohio River.
