Final answer:
Plastic piping is classified into two groups: thermoplastics, which are recyclable and can be reshaped, and thermosets, which permanently harden after heating and cannot be reshaped. The student's question appears to be based on Plastic Identification Codes, not broad classifications of piping.
Step-by-step explanation:
The two broad classifications of plastic piping are thermoplastics and thermosets. Thermoplastics can be reformed after repeated heating and cooling cycles, which makes them recyclable and easy to mold into various shapes. Applications for thermoplastic pipes include water pipes, gas and fire pipelines, electrical and communications conduit, and other products such as milk, juice, and water bottles. On the other hand, thermosets harden permanently after being heated and cannot be reshaped or recycled easily. Common uses for thermoset pipes are in applications that require durable and high-strength materials that can withstand high temperatures.
The student question regarding the classifications does not provide the correct answer format as it appears to reference specific categories or numbers, possibly referring to the Plastic Identification Codes (PICs), which classify seven groups of plastic polymers used for packaging. However, the given options (a through e) do not correctly correspond to the broad classifications for plastic piping.
Recycled plastics are labeled with numbers or letters indicating their PIC. For example, low-density polyethylene is marked with the number "4" or "LDPE," whereas different plastics such as polystyrene and Orlon have different compositions and are used for varying applications based on their properties.