____________ are composed of long chains of polymers that are tangled and can be easily pulled apart by the application of tensile stress. These can easily be recycled. ____________ are composed of long chains of polymers that are strongly cross-linked to one another. These are difficult to recycle.
 a. Thermoplastics, Thermosetting polymers
 b. Thermosetting polymers, Elastomers
 c. Thermosetting polymers, Thermoplastics
 d. Elastomers, Thermoplastics