The $\mathrm{C}-\mathrm{C}$ Sigma Bond in Acetylene Is Formed by the Overlap of Overlap

The $\mathrm{C}-\mathrm{C}$ sigma bond in acetylene is formed by the overlap of which two orbitals?
$\mathrm{H}-\mathrm{C} \equiv \mathrm{C}-\mathrm{H}$

A) $2 \mathrm{p}-2 \mathrm{p}$
B) $\mathrm{sp}-\mathrm{sp}$
C) $\mathrm{sp}^{2}-\mathrm{sp}^{2}$
D) $\mathrm{sp}^{3}-\mathrm{sp}^{3}$