Direction: In the following passage, some of the words have been left out. First read the passage over and try to understand what it is about. Then fill in the blanks with the help of the alternatives given.

The true elixir of life near to our hands is the commonest of all liquids, plain water. It has ___441___ a role of vast significance in ___442___ the course of earth's history and ___443___ to play the leading role in the ___444___ of life on the surface of our ___445___ . Indeed, there is nothing here which ___446___ so much to the beauty of the ___447___as water, be it just a little ___448___ trickling over the rocks or a __449___ pond by the way
side where animals __450___ their thirst.