Sulfuric acid symmetry point group
In fact, you can see $C_2$ and other symmetry elements for yourself in 3D by opening the CIF [1, COD-2005680] with Mercury (free, available for Windows, Linux, MacOS):



Figure 1.
Unit cell of crystalline sulfuric acid $\ce{H2SO4}$.
Green lines parallel to crystallographic axis $b$ depict $C_2$ rotation axes.

This can be achieved by drawing the unit cell content with Calculate → Packing/Slicing…  and adding symmetry elements of interest via Display → Symmetry Elements….



Figure 2.
Single molecular unit $\ce{H2SO4}$ in two projections with the $C_2$ placed in drawing plane (left) and perpendicular to drawing plane (right).

References


Kemnitz, E.; Werner, C.; Trojanov, S. Reinvestigation of Crystalline Sulfuric Acid and Oxonium Hydrogensulfate. Acta Crystallographica Section C Crystal Structure Communications 1996, 52 (11), 2665–2668. https://doi.org/10.1107/S0108270196006749.