関連ワード:  what are the three types of planets    what are the three types of planets in our solar system    what are the three categories of planets    what are the three classes of planets in our solar system    what are the three types of planetary winds    what are the three types of planetary gearsets    what are the three different types of planets    what are the three main types of planets    what are three types of planetary motion    what are three types of planetary winds explain briefly