문제 내용: 다음 글의 요지로 가장 적절한 것은?
선택지 1: Sponsorship is necessary for a successful career.
선택지 2: Building a good network starts from your accomplishments.
선택지 3: A powerful network is a prerequisite for your achievement.
선택지 4: Your insights and outputs grow as you become an expert
  at networking.