The correct answer is B) Contactors contacts can handle heavier loads than relay contacts. The main difference between a relay and a contactor is the current handling capacity of their contacts. Contactors are designed to handle much higher currents and loads compared to relays. Relay contacts are typically rated for lower current applications, while contactor contacts can safely switch and carry significantly higher currents, allowing them to control larger electrical loads. The other answer choices are incorrect. Relays and contactors are not differentiated by their material composition (A), nor do they control different electrical quantities (C). Lastly, the connection configuration (series or parallel) is not the defining characteristic between the two (D).