A. to inform the audience about the history and origin of solar power.
Explanation:
In this passage, the author's main purpose is to inform the audience about the origins of solar power. The author tells us that the idea of solar power dates back to the 1700s. Moreover, he also traces its development through the 1970s and 1980s. Although the main purpose is to inform of its history, the author also informs us of the advantages of solar power when compared to other sources of energy.
