Directions: Five sentences A,B,C,D and E are given below, you need to rearrange the sentences so that the five sentences can together form a meaningful paragraph.

A. In present times, the tendency for fluctuations in an inhomogeneous medium to grow because of self- gravitation is gravitational instability.

B. The process continues until the small region of gas finally forms a gravitationally bound object.

C. One simple physical concept lies behind the formation of the stars: gravitational instability.

D. It is opposed by pressure forces.

E. Newton first perceived it late in the 17th century.