A body of mass \(m\) is projected with speed \(u\) at an angle \(45^\circ\) with the horizontal. The angular momentum of the body, about the point of projection, when the body is at its highest point, is:
1. \( \dfrac{\sqrt2m u^3}{8g}\)
2. \( \dfrac{\sqrt2m u^3}{9g}\)
3. \( \dfrac{\sqrt2m u^3}{6g}\)
4. \( \dfrac{\sqrt2m u^3}{4g}\)