Any idea ?? Read the excerpt from "Islands in Hot Water."

Therefore, people who live on the islands set a good example by working on solutions. They're switching from fossil fuels. They're finding ways to use renewable energy sources. On some islands, people make fuel from coconut oil. They use it to power cars and boats. Some villages get all of their electricity from solar power. They hope that other countries will follow their lead.

Which word from the excerpt is a signal word?

therefore
solutions
renewable
electricity