Audio Guide：

Stars with different mass usually have different internal structure. Stars with mass larger than the Sun have a higher rate of generating energy from their cores. Therefore, they usually have a convection zone around the core, transferring energy in a faster way through convection. Only when energy comes to the outer radioactive zone, it is transferred through radiation. However, for starts with smaller mass than the Sun, there is only a convection zone to transfer energy between the core and the surface due to a slower rate of energy production. They don’t have a radioactive zone.