Which hybrid orbitals are used by carbon atoms in the following molecules?
$(a)$ $CH_3-CH_3$
$(b)$ $CH_3-CH=CH_2$
$(c)$ $CH_3-CH_2-OH$
$(d)$ $CH_3-CHO$
$(e)$ $CH_3COOH$

(N/A) Both $C_1$ and $C_2$ are $sp^3$ hybridized.
$(b)$ $C_1$ is $sp^3$ hybridized,while $C_2$ and $C_3$ are $sp^2$ hybridized.
$(c)$ Both $C_1$ and $C_2$ are $sp^3$ hybridized.
$(d)$ $C_1$ is $sp^3$ hybridized and $C_2$ is $sp^2$ hybridized.
$(e)$ $C_1$ is $sp^3$ hybridized and $C_2$ is $sp^2$ hybridized.