a borderline case的用法和样例：
- I'm not sure whether to pass him or fail him; he's a borderline case.
- Anne will certainly pass the exam, but Susan is a borderline case.
- And kindly note this may be a good example as a borderline case, the forum forbid commercial advertisement, although from my own judgement I think this is not.
- This gives him a borderline triangular face shape.