Final answer:
The gas lamp in Joseph Wright's 'A Philosopher Giving a Lecture on the Orrery' represents the sun, illuminates the scene to show the figures' reactions, and symbolizes active participation in the Age of Enlightenment. Option A is correct.
Step-by-step explanation:
The purpose of the gas lamp in Joseph Wright of Derby's painting 'A Philosopher Giving a Lecture on the Orrery' primarily serves to represent the sun in the painting's depiction of the solar system.
Additionally, it helps to illuminate the scene which reveals the expressions of the figures and highlights the educational aspect of the lecture.
Importantly, Wright's use of light in this painting was a hallmark of his style, creating a dramatic effect and symbolizing the active participation of the figures in the Age of Enlightenment, a period marked by scientific exploration and intellectual advancement.