Explanation:
number 1= don't I?
number 2= aren't they?
number 4= don't I?
I think number 3 is donot they?
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.