user: You are a structured reasoning expert tasked with solving problems step by step. 
You first think about the reasoning process in the mind and then provide the answer. The reasoning process and answer should be enclosed within <think> </think> and <answer> </answer> tags, respectively, i.e., <think> reasoning process here </think> <answer> answer here </answer>. 
Given a question and the associated knowledge graph triplets (entity, relation, entity), you are asked to answer the question with these triplets and your own knowledge. 
You can break down the original question into several sub-questions and explore the given knowledge graph to solve them step-by-step. If there are multiple possible answers, choose one as the final answer. 
After thinking, when you finally reach a conclusion, clearly state the answer within <answer> </answer> tags, i.e., <answer> answer here </answer>. 
Question: Who is the golfer of the 2015 WCG-Cadillac Championship? 
Knowledge Triplets: Dustin Johnson, people.person.education, m.0n1k31h
Dustin Johnson, award.competitor.competitions, 2014 Open Championship (British Open)
Dustin Johnson, award.competitor.competitions_won, 2015 WGC-Cadillac Championship
Columbia, base.biblioness.bibs_location.country, United States of America
Dustin Johnson, common.topic.article, m.04n4sw8
m.0j2gkm6, base.schemastaging.golfer_caddie_relationship.golfer, Dustin Johnson
Dustin Johnson, people.person.gender, Male
2015 WGC-Cadillac Championship, award.competition.winner, Dustin Johnson
Columbia, location.hud_county_place.place, Columbia
m.0wpd79b, celebrities.romantic_relationship.celebrity, Dustin Johnson
Dustin Johnson, people.person.place_of_birth, Columbia
Dustin Johnson, people.person.profession, Golfer
m.0n1k31h, education.education.student, Dustin Johnson
Dustin Johnson, common.topic.notable_for, g.1258s89jq
m.0j19gcr, people.marriage.spouse, Dustin Johnson
Dustin Johnson, celebrities.celebrity.sexual_relationships, m.0wpd79b
Dustin Johnson, common.topic.notable_types, Celebrity
Dustin Johnson, people.person.nationality, United States of America
United States of America, base.biblioness.bibs_topic.is_really, United States of America
Columbia, location.location.containedby, United States of America
Dustin Johnson, people.person.spouse_s, m.0j19gcr
United States of America, base.biblioness.bibs_topic.subsumes, United States of America
m.0d651cn, sports.pro_sports_played.athlete, Dustin Johnson
2015 WGC-Cadillac Championship, award.competition.winner, Dustin Johnson
Dustin Johnson, common.topic.image, Dustin Johnson 2008 US Open cropped
Dustin Johnson, sports.pro_athlete.sports_played_professionally, m.0d651cn
Dustin Johnson, people.person.profession, Golfer
Dustin Johnson, base.schemastaging.golfer_extra.caddies, m.0j2gkm6

Answer: Golfer