Concept:The correct word must fit grammatically after "any" to describe "person".Explanation:"Any" is used here with a singular countable noun.The blank requires an adjective to qualify "person"."Maturing" is a participle, "matured" is a past form, and "matures" is a verb.Only "mature" is the correct base adjective form.Thus, the sentence reads: "I don't believe that any mature person would do such a thing."Answer:Option B. mature