Answer
Please see the work below.
Work Step by Step
a) In Carbon monoxide $CO$, there is a triple bond between carbon and oxygen. The triple bond shows that there are two pi bonds and one sigma bond between carbon and oxygen. Hence the hybridization of Carbon in $CO$ is $sp$.
b) In Carbon dioxide $CO_{2}$, there are double bonds between the carbon atom and two oxygen atoms. Hence the hybridization of Carbon in $CO_{2}$ is $sp^{2}$.
c) In Cyanide $CN^{-}$, there is a triple bond between carbon and nitrogen. The triple bond shows that there are two pi bonds and one sigma bond between carbon and nitrogen. Hence the hybridization of Carbon in $CN^{-}$ is $sp$.
