Final answer:
Copper would be the best choice for a heat exchanger to remove energy from a motor quickly due to its high thermal conductivity, making it an excellent thermal conductor among the provided options.
Step-by-step explanation:
If you are designing a heat exchanger to remove energy from a motor as quickly as possible, the most effective material would be one with the highest thermal conductivity. Based on the provided information, copper commonly has a high thermal conductivity among the options given, meaning it is an excellent thermal conductor and can transfer heat rapidly. Therefore, for the heat exchanger, copper (a) would be the best choice compared to glass (b), steel (c), or polystyrene (d).
What makes copper such an efficient choice is its high thermal conductivity. This property allows it to transfer heat away from the motor quickly to the air via the heat exchanger. Although other metals such as aluminum, gold, and silver also have high thermal conductivities, in the context of this question, copper stands out among the provided options.