41.  In our modern society computers play an important role.

42.  In a word, computers are playing an important role in our society.

43.  Without it, we can not make our lives meaningful and colourful.Library is a wonderful place for people to buy or read books specially in higher educational institutes, libraries play an important role in wider the students' knowledge .

44.  It played an important role in the development of our society, especially the development of commerce.

45.  The construction of four modernization in our country demands a great number of talented people as they play a key role in science, technology, economy and many other fields.

46.  In short, electricity plays a key role in our life .

47.  On the whole, electricity plays a extremely important role in our society, especial in the modern society.

48.  lectricity plays such an important role in our society that it's a great loss of energy that many people waste it.

49.  Paper, which is one of the four great inventions of China, is acting an important role in modern world.

50.  And detergent does the most important role in cleaning.