Answer:
C. Describe why solar panels can last for so long without human intervention.
Step-by-step explanation:
The author wanted to show how solar panels do not need constant human maintenance and can function for a long time, without requiring any human being to make repairs or modifications. To prove this point, he uses emergency call boxes as an example, which are usually located on roads where there are few humans who can do anything for them.
In other words, with the paragraphs shown above, the author wanted to show how solar panels can provide energy in a maintenance-free system.