About 74% of earth's surface is covered by water.
A, B AB and O, O being the most useful, because O blood can be given to everyone, but also the most selective, since they can only receive O blood
A blood transfusion might be refused on religious grounds because Jehovah's Witnesses believe that blood is sacred.
Exercise is a subset of physical activity that is planned, structured, and repetitive and has as a final or an intermediate objective the improvement or maintenance of physical fitness. Physical fitness is a set of attributes that are either health- or skill-related.
