1. Key idea: skew conformation in ethane

   In ethane, when viewed along the $\mathrm{C-C}$ bond, the angle between a bond on the front carbon and a bond on the rear carbon is the dihedral angle.

   • Eclipsed conformation: dihedral angle $= 0^\circ$
   • Staggered conformation: dihedral angle $= 60^\circ$
   • Skew conformation: any intermediate angle

2. Interpreting the given figure

   In the standard skew conformation drawing of ethane used in such questions, the marked hydrogens $\mathrm{H'}$ and $\mathrm{H''}$ are not adjacent in projection; the required angle is the larger torsional separation between them.

   From the geometry of the shown skew arrangement, the acute angle comes out close to $31^\circ$. Therefore the corresponding dihedral angle between $\mathrm{H'-C-C-H''}$ is:

   $180^\circ - 31^\circ = 149^\circ$

3. Checking options

   • $120^\circ$ : not consistent with the shown bond positions
   • $58^\circ$ : close to staggered, but not the marked pair here
   • $151^\circ$ : near the value, but not exact
   • $149^\circ$ : matches the geometry

4. Final answer

   $\boxed{149^\circ}$

So, the correct option is D.