Please choose the correct answer to the question: The Milky Way Galaxy is visible as a bright region in the night sky. Modern telescopic observation has made it possible to discover that the brightness of the Milky Way Galaxy is due primarily to which structure?

Answer1: clouds of hot gas Answer2: large numbers of stars Answer3: high energy compounds Answer4: extremely reflective ice particles

Answer format: answer1/answer2/answer3/answer4
Answer: answer2