Please choose the correct answer to the question: A house is built in a desert, where there is no electricity and very little wind. Which action could lead to operating the electrical appliances in the house that would cause the least amount of environmental pollution?

Answer1: constructing a small hydroelectric plant Answer2: placing solar panels on the roof of the house Answer3: using gasoline generators Answer4: burning coal or wood

Answer format: answer1/answer2/answer3/answer4