12.36.    In the organic compound $C\! H_{2}=C\! H-C\! H_{2}-C\! H_{2}- C\equiv \! CH$, the pair of hydridised orbitals involved in the formation of: $C_{2}-C_{3}$ bond is:                $(a) sp-sp^{2}$       $(b) sp-sp^{3}$        $(c) sp^{2}-sp^{3}$       $(d) sp^{3}-sp^{3}$

$C\! H_{2}=C\! H-C\! H_{2}-C\! H_{2}- C\equiv \! CH$
In $C_2$ and $C_3$ carbon atom the hybridisation is $sp^2-sp^3$