Please choose the correct answer to the question: A block of ice is placed on a hot sidewalk. The ice melts because

Answer1: the energy from the ice flows to the sidewalk. Answer2: the energy from the sidewalk flows to the ice. Answer3: convection currents flow between the ice and the sidewalk. Answer4: radiation flows between the ice and the sidewalk.

Answer format: answer1/answer2/answer3/answer4