1. Is the chunk that black appears inside fingernail why? 指甲里面出现黑色的大块是为什么?
2. All round fingernail very easy desquamate, especially fingernail left and right sides, be because, what? 手指甲周围很容易脱皮，特别是指甲左右，是因为什么呢？
3. The effect is easy to observe on a smooth, flat-black material(e. g. poster-painted paper), but you can see it on a fingernail or a worn coin as well. 在一个光滑的、平而黑的材料上（例如招贴画的纸）容易看到这个效应，但是也可以在指甲上或旧的硬币上看到。
