In the molecule $HC^{1} \equiv C^{2} - CH^{3} = CH^{4} - CH_{3}^{5}$,which carbon atom exhibits the lowest electronegativity?

$(a)$ 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:
$(a)$ $\overset{*}{C}H_2 = CH - C(=O)OH$
$(b)$ $CH_3 - \overset{*}{C}H_2 - OH$
$(c)$ $CH_3 - CH_2 - \overset{*}{C}H = O$
$(d)$ $\overset{*}{C}H_3 - CH = CH - CH_3$
$(e)$ $CH_3 - \overset{*}{C} \equiv CH$

Consider a positively charged $C_2H_3$ species in which the positively charged carbon is $sp$-hybridized,the uncharged carbon is $sp^2$-hybridized and an empty $p$-orbital is perpendicular to the $\pi$ system. What is the best description of this cation?

How many $(i)$ $sp^{2}$ hybridised carbon atoms and $(ii)$ $\pi$ bonds are present in the following compound?

The hybridization of $C_2$ and $C_3$ in $CH_3-CH=C=CH-CH_3$ is

Which among the following possesses a $sp$ carbon in its structure?