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Dear student,

Please ask single question in single thread.

4) 

Conservation refers to the controlled and sustainable use like that of natural resources so that it can be used by the future generation. Preservation on the other hand is the act of keeping safe or free from harm or decay. Thus conservation means keeping things as it is.

Also, to preserve an object means to protect it from change and to conserve an object, on the other hand, means to use an object judicially with the knowledge that it could run out.

 6) Dear Student, 
Advantages of synthetic fibers:

• They are cheap.
• They are durable.
• Do not wrinkle easily.
• Most have good elasticity.
• They dry up quickly.
• Are easily available.
• They are easy to maintain and can carry heavy loads.

Regards