19.Nuclear Power
For：
1. it provides huge amounts of energy from small amounts of fuel
2. the world' s supply of oil will be exhausted in 90 years
3. it could supply all the world' s electricity for millions of years if fully developed
4. nuclear power plants create less air pollution than fossil-fuel power plants
20. Library: Computer V.S. Books
Computer:
For:
1) Efficiency
2) Large storage capacity
3) Multimedia attraction
5) Sharing information
6) Network or Internet
7) Rapid updating
Books:
For:
1) Traditional medium
2) Easy to carry
3) Conveniently read
4) index of academic environment
Against:
1) Not durable
2) Low rate of updating
3) Can't be shared by any people