Which of the following statements is incorrect?

Since four electrons are in the pi orbitals ${\mathrm{C}}_2$ contains only pi bond. While in there is a triple bond between the atoms there is 1 sigma bond $2\pi$ bonds.

According to the "metal electron sea model," each metal atom in a metallic solid contributes one of its valence electrons, which float and create an "electronic sea" around the metal atoms.

Hence, option D is correct.