An iron bar is placed in a flame, as shown below, and is heated until the end glows. The other end of the iron bar
soon becomes hot, too. Which of the following statements best describes what happens?

a. Radiation moves through the iron bar and is absorbed by the end not in the flame.
b. A convective flow of energy is set up inside the iron bar.
c. Energy is conducted from atom to atom along the length of the iron bar.
d. Air heated by the flame radiates down the iron bar and heats the end not in the flame.