题干
Mike used to be a top student, but he ______ behind since he lost himself in computer games.
A：fell
B：has fallen
C：was
D：has been
答案(点此获取答案解析）
D
Mike used to be a top student, but he ______ behind since he lost himself in computer games.
A：fell
B：has fallen
C：was
D：has been
