The (C – H) bond length order in hydro-carbons in which the hybridisation of carbon is sp³ or sp² or sp

Bond Order is directly proportional to Bond Strength and inversely proportional to Bond Length (stronger is the bond, more is the B.O. and smaller is the B.L.)

In sp³ – s bond, B.O. = 1 $(\mathrm{C}-\mathrm{C})$

In sp² – s bond, B.O. = 2 $(\mathrm{C}=\mathrm{C})$

In sp – s bond, B.O. =  3 $(\mathrm{C}\equiv \mathrm{C})$

Thus, B.L. = sp³ – s > sp² – s > sp – s.

Hence, the correct option is option (C) sp³ – s > sp² – s > sp – s.