Because the problem there is just as severe, but it is more sinister, because vitamin D deficiency, from a lack of ultraviolet B radiation, is a major problem.
所面临的问题。 他们所面临的问题是同等严重的。 不过却更加不宜察觉。 因为紫外线B辐射不足 所引发的维生素D短缺 是一个重大的问题。