2010년 고등학교 1학년 3월 모의고사 문법 문제 중에서 이해가 되지 않아서 질문합니다..22. 다음 중 어법상 어색한 것은??After moving to a new city, I ①joined the company baseball team. Being the oldest player, I had to play the outfield. During one game, I made a ②few mistakes. Then I kept ③hearing someone shouting, “Way to go, Mr. Green” and “You can do it, Mr. Green.” I was amazed someone would know my name in this strange city. After the game, I met my wife and son and asked ④that they knew who was shouting encouragement in the stand. My son spoke up and said, “Dad, it was me.” I asked why he was calling me Mr. Green and he replied, “I didn’t want anyone ⑤to know that I’m your son.”

정답은 4번 그이유는 무엇인지??
그러면 어떻게 고쳐야 하는지 알려주세요^^