Directions: Read the following passage carefully and answer the questions given below it.
One simple concept lies behind the formation of the stars: gravitational instability. The concept is not new. Newton first perceived it late in the 17th Century. Imagine a uniform, static cloud of gas in space. Imagine then that the gas is somehow disturbed so that one small spherical region becomes a little denser than the gas around it so that the small region's gravitational field becomes slightly stronger. It now attracts more matter to it and its gravity increases further causing it to begin to contract. As it contracts its density increases, which increases its gravity even more so that it picks up even more matter and contracts even further. The process continues until the small region of gas finally forms a gravitationally bound object.