It is true about polymers: a) - They are light-weight materials b) - There are three general classes: thermosets, thermoplastics and thermoset c) - They present long term instability under load d) - All the above

Answer: d) All of the above

Explanation: Polymers are the substances that have molecular structure with having same bonds in the entire molecule together. There are light weight substance which occur natural as well as artificially. They are also categorized as thermoplastics, thermosets, and elastomers. They also have the property of being stretching and bending under the pressure or load they are also instable. Therefore, all the options are correct statement about polymers.