If the left front park light is not functioning, which of the following is least likely to be the cause?

The least likely cause of a malfunctioning left front park light being the switch can be attributed to the fact that the switch typically controls multiple lights. If the switch were faulty, it would likely affect all the lights that it controls rather than just one specific bulb. This means that if the left front park light is the only one not functioning, it suggests that the issue lies closer to that particular light's circuit, such as in the bulb, ground, or light socket.

Conversely, a bad bulb is often a common issue for non-functioning lights, as bulbs have a limited lifespan and can burn out. Similarly, a bad ground connection can prevent the circuit from completing, leading to an inoperative light, and a bad light socket could inhibit the proper connection and function of the bulb. These components are more directly related to the individual light’s operation. Thus, while a bad switch can cause lighting issues, it is less likely to be the singular cause of a single park light malfunctioning, making it the least probable cause in this scenario.