Likewise, fans (who only ponder what athletes owe them without ever reflecting on what they owe to athletes) (B) [has / have] neglected to treat the fan/athlete relationship with due seriousness. 관계대명사절을 정리하면 주어가 fans가 됩니다. 복수명사이기 때문에 동사는 복수 have가 됩니다 !