Final answer:
Line voltage thermostats with heavier contacts can use all the mentioned sensing elements, including bimetallic strip, bellows, and remote bulb, to detect temperature changes.
Step-by-step explanation:
Line voltage thermostats use different types of sensing elements to control heating and cooling systems. A line voltage thermostat with heavier contacts may use various sensing elements such as a bimetallic strip, which consists of two different metals bonded together that expand and contract at different rates. This causes the strip to bend and activate the switch mechanism in response to temperature changes. Other types of sensing elements include bellows and remote bulb sensors; therefore, the correct answer is d. all of the above.