Fill blank (viii).

Directions: Read the following passage having some numbered blanks.

Many people have sacrificed their lives to ___(i)___ the thirst for knowledge and to satisfy their ___(ii)___. In the olden days people used to worship sun and moon thinking them to be ___(iii)___ heav­enly bodies. But the scientific investigation had ___(iv)___ that sun is an ordinary star and earth is a planet like other planets. After this, man entered the age of the space travel. The invention of rocket was the first step in space travel. Scientists had already ___(v)___ that there was neither air nor water on the moon. The moon was the first ___(vi)___ of man. A spaceship travel­ling at a speed of 4000 kms per hour can ___(vii)___ this distance in 10 hours. The scientists had ___(viii)___ discovered that the surface of moon was rough and full of craters, rocks and mountains. Scientists now are trying to find out whether there is life on Mars and they are planning to ___(ix)___ it also. Many centuries after that space travel would be taken as an ___(x)___ by the rich people of the world who can afford a huge amount for satiating their whims.