Oh, that is why the net electric flux  through the right triangular box was zero.

哦，这就是为什么穿过直角三角盒的净电通量为零。

I will also point out that, if the net charge  inside a closed Gaussian surface is zero, then the net electric flux through  the Gaussian surface is also zero.

我还要指出，如果封闭高斯曲面内的净电荷为零，则穿过高斯曲面的净电通量也为零。