In Musèe des Beaux Arts by W.H. Auden the people on the ship do nothing after seeing Icarus fall into the sea and the ship continues on its way. Why was that? Because according to the author, when a tragedy happens, human beings are not affected by it if their interests are protected and they have an horizon to pursue.
Your first option is correct.
EXPLANATION:
your first option is correct because this is a grammar question. When you use "an" you're using it in front of a vowel. The only sentence starting with a vowel is the first one. The others don't sound right when you use "an" in front of it instead of "a".
I hope I helped! :)
Answer:
It is because solar power illustrate the flow
Compound!
I hope this helps
