Which statement best describes the structure of the allene molecule, ${\mathrm{H}}_2\mathrm{C}=\mathrm{C}={\mathrm{CH}}_2$ ?

The C atoms form an angle of 180° and the two ${\mathrm{CH}}_2$ groups are perpendicular to one another

The C atoms form an angle of 120° and the H atoms lie in the same plane as the C atoms.

The C atoms form an angle of 120° and the H atoms lie in a plane perpendicular to that of the C atoms.

The C atoms form an angle of 180° and the four H atoms lie in the same plane