In the compound $CH_2 = CH - CH_2 - CH_2 - C \equiv CH$,the $C_2 - C_3$ bond is of the type

The hybridization of carbon atoms in buta-$1,2$-diene is of the type........

Number of $sp$ hybridised carbon atoms in the given compound is:
$CH_2 = CH - C \equiv C - CH_2 - CN$

$(a)$ Discuss the concept of hybridization. What are its different types in a carbon atom.
$(b)$ What is the type of hybridization of carbon atoms marked with a star in the following structures:
$(a)$ $\overset{*}{C}H_2 = CH - C(=O)OH$
$(b)$ $CH_3 - \overset{*}{C}H_2 - OH$
$(c)$ $CH_3 - CH_2 - \overset{*}{C}H = O$
$(d)$ $\overset{*}{C}H_3 - CH = CH - CH_3$
$(e)$ $CH_3 - \overset{*}{C} \equiv CH$

The bond between carbon atom $(1)$ and carbon atom $(2)$ in compound $N \equiv C - CH = CH_2$ involves the hybridised carbon as

Which of the following represents the given mode of hybridization $sp^2 - sp^2 - sp - sp$ from left to right?