题干
— I find it difficult to learn Physics well.
— That's true. Nobody can learn it well _______ he works hard at it.
A：if
B：because
C：unless
答案(点此获取答案解析）
C
— I find it difficult to learn Physics well.
— That's true. Nobody can learn it well _______ he works hard at it.
A：if
B：because
C：unless
