Which of the following molecules is tetrahedral?

What is meant by hybridisation? The compound $CH_2 = C = CH_2$ contains $sp$ and $sp^2$ hybridised carbon atoms. Will it be a planar molecule?

Identify the molecules which have $sp$-hybridised carbon$(s)$ from the list given below:
$I$. Ethane nitrile $(CH_3CN)$
$II$. Buta$-1,3-$diene $(CH_2=CH-CH=CH_2)$
$III$. Propan$-1,2-$diene $(CH_2=C=CH_2)$
$IV$. Ethyne $(HC \equiv CH)$
$V$. Benzene $(C_6H_6)$

In which of the following reactions does the hybridization of the central atom change from $sp^2$ to $sp^3$?

In which of the following sets of molecules,do the central atoms have the same hybridisation?

Give an example and explain the meaning of hybridization.