How many degrees of unsaturation are there in the following compound?

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

Write the importance of organic chemistry.

Two unknown compounds $X$ and $Y$,both having molecular formula $C_4H_8O$,give the following results with four chemical tests.

Compound	Bromine	$Na$ metal	Chromic acid	Lucas reagent
$X$	decolourises	bubbles	Orange to Green	No reaction
$Y$	No reaction	No reaction	No reaction	No reaction

Compound $X$ and $Y$ respectively are:

Given below are two statements:
Statement-$I$ : Compound $(X)$, shown below, dissolves in $NaHCO_3$ solution and has two chiral carbon atoms.
Statement-$II$ : Compound $(Y)$, shown below, has two carbons with $sp^3$ hybridization, one carbon with $sp^2$ and one carbon with $sp$ hybridization.
In the light of the above statements, choose the correct answer from the options given below:

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.