1.  Copper is not usually a natural component of water and is picked up by contact with copper and brass fittings or pipes.

2.  All were members of political clans, which more or less considered the presidency a natural component of the family business.

3.  Cannabidiol, a natural component of the marijuana plant, shows promise as a potential treatment for stroke, say researchers who tested it in rat brains.

4.  For it is the natural components of their sculpture that remains in the mind after leaving the show, not the geometry.

5.  Unlike nicotine, the addictive compound in cigarettes, tar is not a natural component of tobacco.

6.  Methane is a natural component of most coal seams.