What type (s) of orbital overlap is (are) indicated on the left most carbon of allene, which is shown below? h2c=c=ch2?

Allene:

H₂C=C=CH₂,

In it central carbon is sp hybrised while left carbon is sp² hybridised.

So there is a presence of three sigma and one pi bond on the left bonded carbon of allene.

And there is a presence of sp² hybridised orbital on the left most carbon of allene. or we can say there is presence of 3 sigma and one pi bonding orbitals on the left most carbon of allene.