Which compound contains $1^o, 2^o, 3^o$ and $4^o$ carbon atoms?

Homologues have different

The enolic form of acetone contains:

Fill in the blanks:
$(1)$ Two isomers of butane are $n$-butane and isobutane. The relation of the number of $\sigma$ and $\pi$-bonds in them is .......... .
$(2)$ .......... is present in the structure of a heterocyclic compound.
$(3)$ Cyclohexene is a .......... type and furan is a .......... type of compound.
$(4)$ .......... type of $3-D$ model indicates the atomic volume but does not indicate the bond.

State whether the following statements are True or False:
$(i)$ There is a huge number of organic compounds because the carbon atom is very small.
$(ii)$ The number of organic compounds is huge because of catenation.
$(iii)$ Organic compounds are in a huge number because of valency.

What do the solid wedge and dashed wedge symbols indicate in the 3D representation of an organic molecule?