radius of sphere

例句：

1. 1. The circle has a radius of 10 units.
   这个圆的半径是10单位。
2. 2. The diameter of the circle is twice its radius.
   这个圆的直径是半径的两倍。
3. 3.The circumference of the circle is equal to its radius times two.
   这个圆的周长等于半径的两倍。