1. The Earth was formed about five billion years ago from a rotating, circular cloud of dust and gases such as hydrogen and nitrogen.
    地球的形成约在50亿年前，起源于一团循环旋转的尘埃和诸如氢、氧之类的气体。

2. A wheel is circular.
    轮子是圆形的。

3. An ocean wave passing through deep water causes a particle on the surface to move in a roughly circular orbit, drawing the particle first towards the advancing wave,
    穿过深水的海浪使水面上的一个微粒按照一种近乎圆形的轨道移动，先把微粒拉向前移动的海浪，