Which of the following statements is correct in the context of the allene molecule, ${\mathrm{C}}_3{\mathrm{H}}_4$ ?

Solution:

The central C atom in the allene molecule is sp hybridised, and the remaining two C atoms are $s{p}^2$ hybridised.
As a result, the central C atom possesses two double bonds, compared to just one double bond for each of the other two C atoms.
On the centre carbon atom, there are two unhybridized, mutually perpendicular p orbitals. Two pi bonds are created between these two unhybridized p orbitals and two nearby C atoms.
As a result, the planes that include the ${\mathrm{CH}}_2$ groups are perpendicular to one another.