对于任意完全包含在圆环面上的曲面，这个曲线都不是它的边界。

See, this one also does not bound anything that's completely contained in the torus.

youdao

对于任意完全包含在圆环面上的曲面，这个曲线都不是它的边界。

See, this one also does not bound anything that's completely contained in the torus.

youdao